diff --git a/lib/chain/chain.js b/lib/chain/chain.js
index 39d11bed..92e2004d 100644
--- a/lib/chain/chain.js
+++ b/lib/chain/chain.js
@@ -15,6 +15,7 @@ var assert = utils.assert;
 var VerifyError = bcoin.errors.VerifyError;
 var VerifyResult = utils.VerifyResult;
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 
 /**
  * Represents a blockchain.
@@ -183,7 +184,7 @@ Chain.prototype._init = function _init() {
  * @param {Function} callback
  */
 
-Chain.prototype._open = spawn.co(function* open() {
+Chain.prototype._open = co(function* open() {
   var tip;
 
   this.logger.info('Chain is loading.');
@@ -252,7 +253,7 @@ Chain.prototype._lock = function _lock(block, force) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.verifyContext = spawn.co(function* verifyContext(block, prev) {
+Chain.prototype.verifyContext = co(function* verifyContext(block, prev) {
   var state, view;
 
   state = yield this.verify(block, prev);
@@ -288,7 +289,7 @@ Chain.prototype.isGenesis = function isGenesis(block) {
  * [{@link VerifyError}, {@link VerifyFlags}].
  */
 
-Chain.prototype.verify = spawn.co(function* verify(block, prev) {
+Chain.prototype.verify = co(function* verify(block, prev) {
   var ret = new VerifyResult();
   var i, height, ts, tx, medianTime, commitmentHash, ancestors, state;
 
@@ -418,7 +419,7 @@ Chain.prototype.verify = spawn.co(function* verify(block, prev) {
  * [{@link VerifyError}, {@link DeploymentState}].
  */
 
-Chain.prototype.getDeployments = spawn.co(function* getDeployments(block, prev, ancestors) {
+Chain.prototype.getDeployments = co(function* getDeployments(block, prev, ancestors) {
   var state = new DeploymentState();
   var active;
 
@@ -527,7 +528,7 @@ Chain.prototype.getDeployments = spawn.co(function* getDeployments(block, prev,
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.checkDuplicates = spawn.co(function* checkDuplicates(block, prev) {
+Chain.prototype.checkDuplicates = co(function* checkDuplicates(block, prev) {
   var height = prev.height + 1;
   var entry;
 
@@ -568,7 +569,7 @@ Chain.prototype.checkDuplicates = spawn.co(function* checkDuplicates(block, prev
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.findDuplicates = spawn.co(function* findDuplicates(block, prev) {
+Chain.prototype.findDuplicates = co(function* findDuplicates(block, prev) {
   var height = prev.height + 1;
   var i, tx, result;
 
@@ -607,7 +608,7 @@ Chain.prototype.findDuplicates = spawn.co(function* findDuplicates(block, prev)
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.checkInputs = spawn.co(function* checkInputs(block, prev, state) {
+Chain.prototype.checkInputs = co(function* checkInputs(block, prev, state) {
   var height = prev.height + 1;
   var historical = prev.isHistorical();
   var sigops = 0;
@@ -731,7 +732,7 @@ Chain.prototype._getCachedHeight = function _getCachedHeight(hash) {
  * @param {Function} callback - Returns [{@link Error}, {@link ChainEntry}].
  */
 
-Chain.prototype.findFork = spawn.co(function* findFork(fork, longer) {
+Chain.prototype.findFork = co(function* findFork(fork, longer) {
   while (fork.hash !== longer.hash) {
     while (longer.height > fork.height) {
       longer = yield longer.getPrevious();
@@ -761,7 +762,7 @@ Chain.prototype.findFork = spawn.co(function* findFork(fork, longer) {
  * @param {Function} callback
  */
 
-Chain.prototype.reorganize = spawn.co(function* reorganize(entry, block) {
+Chain.prototype.reorganize = co(function* reorganize(entry, block) {
   var tip = this.tip;
   var fork = yield this.findFork(tip, entry);
   var disconnect = [];
@@ -807,7 +808,7 @@ Chain.prototype.reorganize = spawn.co(function* reorganize(entry, block) {
  * @param {Function} callback
  */
 
-Chain.prototype.disconnect = spawn.co(function* disconnect(entry) {
+Chain.prototype.disconnect = co(function* disconnect(entry) {
   var items = yield this.db.disconnect(entry);
   var block = items[1];
   var prev = yield entry.getPrevious();
@@ -833,7 +834,7 @@ Chain.prototype.disconnect = spawn.co(function* disconnect(entry) {
  * @param {Function} callback
  */
 
-Chain.prototype.reconnect = spawn.co(function* reconnect(entry) {
+Chain.prototype.reconnect = co(function* reconnect(entry) {
   var block = yield this.db.getBlock(entry.hash);
   var prev, view;
 
@@ -880,7 +881,7 @@ Chain.prototype.reconnect = spawn.co(function* reconnect(entry) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.setBestChain = spawn.co(function* setBestChain(entry, block, prev) {
+Chain.prototype.setBestChain = co(function* setBestChain(entry, block, prev) {
   var view;
 
   assert(this.tip);
@@ -929,7 +930,7 @@ Chain.prototype.setBestChain = spawn.co(function* setBestChain(entry, block, pre
  * @param {Function} callback
  */
 
-Chain.prototype.reset = spawn.co(function* reset(height, force) {
+Chain.prototype.reset = co(function* reset(height, force) {
   var unlock = yield this._lock(null, force);
   var result;
 
@@ -957,7 +958,7 @@ Chain.prototype.reset = spawn.co(function* reset(height, force) {
  * @param {Function} callback
  */
 
-Chain.prototype.resetTime = spawn.co(function* resetTime(ts) {
+Chain.prototype.resetTime = co(function* resetTime(ts) {
   var unlock = yield this._lock();
   var entry = yield this.byTime(ts);
 
@@ -998,7 +999,7 @@ Chain.prototype.isBusy = function isBusy() {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Chain.prototype.add = spawn.co(function* add(block) {
+Chain.prototype.add = co(function* add(block) {
   var ret, unlock, initial, hash, prevBlock;
   var height, checkpoint, orphan, entry;
   var existing, prev;
@@ -1363,7 +1364,7 @@ Chain.prototype.pruneOrphans = function pruneOrphans() {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-Chain.prototype.has = spawn.co(function* has(hash) {
+Chain.prototype.has = co(function* has(hash) {
   if (this.hasOrphan(hash))
     return true;
 
@@ -1382,7 +1383,7 @@ Chain.prototype.has = spawn.co(function* has(hash) {
  * @param {Function} callback - Returns [Error, {@link ChainEntry}].
  */
 
-Chain.prototype.byTime = spawn.co(function* byTime(ts) {
+Chain.prototype.byTime = co(function* byTime(ts) {
   var start = 0;
   var end = this.height;
   var pos, delta, entry;
@@ -1521,7 +1522,7 @@ Chain.prototype.getProgress = function getProgress() {
  * @param {Function} callback - Returns [Error, {@link Hash}[]].
  */
 
-Chain.prototype.getLocator = spawn.co(function* getLocator(start) {
+Chain.prototype.getLocator = co(function* getLocator(start) {
   var unlock = yield this._lock();
   var hashes = [];
   var step = 1;
@@ -1609,7 +1610,7 @@ Chain.prototype.getOrphanRoot = function getOrphanRoot(hash) {
  * (target is in compact/mantissa form).
  */
 
-Chain.prototype.getCurrentTarget = spawn.co(function* getCurrentTarget() {
+Chain.prototype.getCurrentTarget = co(function* getCurrentTarget() {
   if (!this.tip)
     return this.network.pow.bits;
   return yield this.getTargetAsync(null, this.tip);
@@ -1623,7 +1624,7 @@ Chain.prototype.getCurrentTarget = spawn.co(function* getCurrentTarget() {
  * (target is in compact/mantissa form).
  */
 
-Chain.prototype.getTargetAsync = spawn.co(function* getTargetAsync(block, prev) {
+Chain.prototype.getTargetAsync = co(function* getTargetAsync(block, prev) {
   var ancestors;
 
   if ((prev.height + 1) % this.network.pow.retargetInterval !== 0) {
@@ -1718,7 +1719,7 @@ Chain.prototype.retarget = function retarget(prev, first) {
  * hash of the latest known block).
  */
 
-Chain.prototype.findLocator = spawn.co(function* findLocator(locator) {
+Chain.prototype.findLocator = co(function* findLocator(locator) {
   var i, hash, main;
 
   for (i = 0; i < locator.length; i++) {
@@ -1742,7 +1743,7 @@ Chain.prototype.findLocator = spawn.co(function* findLocator(locator) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-Chain.prototype.isActive = spawn.co(function* isActive(prev, id) {
+Chain.prototype.isActive = co(function* isActive(prev, id) {
   var state;
 
   if (prev.isHistorical())
@@ -1763,7 +1764,7 @@ Chain.prototype.isActive = spawn.co(function* isActive(prev, id) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-Chain.prototype.getState = spawn.co(function* getState(prev, id) {
+Chain.prototype.getState = co(function* getState(prev, id) {
   var period = this.network.minerWindow;
   var threshold = this.network.activationThreshold;
   var deployment = this.network.deployments[id];
@@ -1888,7 +1889,7 @@ Chain.prototype.getState = spawn.co(function* getState(prev, id) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-Chain.prototype.computeBlockVersion = spawn.co(function* computeBlockVersion(prev) {
+Chain.prototype.computeBlockVersion = co(function* computeBlockVersion(prev) {
   var keys = Object.keys(this.network.deployments);
   var version = 0;
   var i, id, deployment, state;
@@ -1916,7 +1917,7 @@ Chain.prototype.computeBlockVersion = spawn.co(function* computeBlockVersion(pre
  * @param {Function} callback - Returns [Error, {@link DeploymentState}].
  */
 
-Chain.prototype.getDeploymentState = spawn.co(function* getDeploymentState() {
+Chain.prototype.getDeploymentState = co(function* getDeploymentState() {
   var prev, ancestors;
 
   if (!this.tip)
@@ -1941,7 +1942,7 @@ Chain.prototype.getDeploymentState = spawn.co(function* getDeploymentState() {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-Chain.prototype.checkFinal = spawn.co(function* checkFinal(prev, tx, flags) {
+Chain.prototype.checkFinal = co(function* checkFinal(prev, tx, flags) {
   var height = prev.height + 1;
   var ts;
 
@@ -1966,7 +1967,7 @@ Chain.prototype.checkFinal = spawn.co(function* checkFinal(prev, tx, flags) {
  * [Error, Number(minTime), Number(minHeight)].
  */
 
-Chain.prototype.getLocks = spawn.co(function* getLocks(prev, tx, flags) {
+Chain.prototype.getLocks = co(function* getLocks(prev, tx, flags) {
   var mask = constants.sequence.MASK;
   var granularity = constants.sequence.GRANULARITY;
   var disableFlag = constants.sequence.DISABLE_FLAG;
@@ -2015,7 +2016,7 @@ Chain.prototype.getLocks = spawn.co(function* getLocks(prev, tx, flags) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-Chain.prototype.evalLocks = spawn.co(function* evalLocks(prev, minHeight, minTime) {
+Chain.prototype.evalLocks = co(function* evalLocks(prev, minHeight, minTime) {
   var medianTime;
 
   if (minHeight >= prev.height + 1)
@@ -2040,7 +2041,7 @@ Chain.prototype.evalLocks = spawn.co(function* evalLocks(prev, minHeight, minTim
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-Chain.prototype.checkLocks = spawn.co(function* checkLocks(prev, tx, flags) {
+Chain.prototype.checkLocks = co(function* checkLocks(prev, tx, flags) {
   var times = yield this.getLocks(prev, tx, flags);
   var minHeight = times[0];
   var minTime = times[1];
diff --git a/lib/chain/chaindb.js b/lib/chain/chaindb.js
index f8a77120..36aca9aa 100644
--- a/lib/chain/chaindb.js
+++ b/lib/chain/chaindb.js
@@ -16,6 +16,7 @@ var DUMMY = new Buffer([0]);
 var BufferWriter = require('../utils/writer');
 var BufferReader = require('../utils/reader');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 
 /*
  * Database Layout:
@@ -214,7 +215,7 @@ ChainDB.layout = layout;
  * @param {Function} callback
  */
 
-ChainDB.prototype._open = spawn.co(function* open() {
+ChainDB.prototype._open = co(function* open() {
   var result, genesis, block;
 
   this.logger.info('Starting chain load.');
@@ -318,7 +319,7 @@ ChainDB.prototype.drop = function drop() {
  * @param {Function} callback
  */
 
-ChainDB.prototype.commit = spawn.co(function* commit() {
+ChainDB.prototype.commit = co(function* commit() {
   assert(this.current);
   assert(this.pending);
 
@@ -389,7 +390,7 @@ ChainDB.prototype.getCache = function getCache(hash) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-ChainDB.prototype.getHeight = spawn.co(function* getHeight(hash) {
+ChainDB.prototype.getHeight = co(function* getHeight(hash) {
   var entry, height;
 
   checkHash(hash);
@@ -423,7 +424,7 @@ ChainDB.prototype.getHeight = spawn.co(function* getHeight(hash) {
  * @param {Function} callback - Returns [Error, {@link Hash}].
  */
 
-ChainDB.prototype.getHash = spawn.co(function* getHash(height) {
+ChainDB.prototype.getHash = co(function* getHash(height) {
   var entry;
 
   checkHash(height);
@@ -447,7 +448,7 @@ ChainDB.prototype.getHash = spawn.co(function* getHash(height) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-ChainDB.prototype.getChainHeight = spawn.co(function* getChainHeight() {
+ChainDB.prototype.getChainHeight = co(function* getChainHeight() {
   var entry = yield this.getTip();
   if (!entry)
     return -1;
@@ -461,7 +462,7 @@ ChainDB.prototype.getChainHeight = spawn.co(function* getChainHeight() {
  * @param {Function} callback - Returns [Error, {@link Hash}, Number].
  */
 
-ChainDB.prototype.getBoth = spawn.co(function* getBoth(block) {
+ChainDB.prototype.getBoth = co(function* getBoth(block) {
   var hash, height;
 
   checkHash(block);
@@ -494,7 +495,7 @@ ChainDB.prototype.getBoth = spawn.co(function* getBoth(block) {
  * @param {Function} callback - Returns [Error, {@link ChainEntry}].
  */
 
-ChainDB.prototype.getEntry = spawn.co(function* getEntry(hash) {
+ChainDB.prototype.getEntry = co(function* getEntry(hash) {
   var self = this;
   var entry;
 
@@ -521,7 +522,7 @@ ChainDB.prototype.getEntry = spawn.co(function* getEntry(hash) {
  * @param {Function} callback - Returns [Error, {@link ChainEntry}].
  */
 
-ChainDB.prototype.get = spawn.co(function* get(hash) {
+ChainDB.prototype.get = co(function* get(hash) {
   var entry = yield this.getEntry(hash);
 
   if (!entry)
@@ -548,7 +549,7 @@ ChainDB.prototype.get = spawn.co(function* get(hash) {
  * @param {Function} callback
  */
 
-ChainDB.prototype.save = spawn.co(function* save(entry, block, view, connect) {
+ChainDB.prototype.save = co(function* save(entry, block, view, connect) {
   var hash = block.hash();
   var height = new Buffer(4);
 
@@ -592,7 +593,7 @@ ChainDB.prototype.save = spawn.co(function* save(entry, block, view, connect) {
  * @param {Function} callback - Returns [Error, {@link ChainState}].
  */
 
-ChainDB.prototype.initState = spawn.co(function* initState() {
+ChainDB.prototype.initState = co(function* initState() {
   var state = yield this.db.fetch(layout.R, function(data) {
     return ChainState.fromRaw(data);
   });
@@ -622,7 +623,7 @@ ChainDB.prototype.getTip = function getTip() {
  * Returns [Error, {@link ChainEntry}, {@link Block}].
  */
 
-ChainDB.prototype.reconnect = spawn.co(function* reconnect(entry, block, view) {
+ChainDB.prototype.reconnect = co(function* reconnect(entry, block, view) {
   var hash = block.hash();
 
   this.start();
@@ -654,7 +655,7 @@ ChainDB.prototype.reconnect = spawn.co(function* reconnect(entry, block, view) {
  * Returns [Error, {@link ChainEntry}, {@link Block}].
  */
 
-ChainDB.prototype.disconnect = spawn.co(function* disconnect(entry) {
+ChainDB.prototype.disconnect = co(function* disconnect(entry) {
   var block;
 
   this.start();
@@ -714,7 +715,7 @@ ChainDB.prototype.getNextHash = function getNextHash(hash) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-ChainDB.prototype.isMainChain = spawn.co(function* isMainChain(hash) {
+ChainDB.prototype.isMainChain = co(function* isMainChain(hash) {
   var query, height, existing;
 
   if (hash instanceof bcoin.chainentry) {
@@ -745,7 +746,7 @@ ChainDB.prototype.isMainChain = spawn.co(function* isMainChain(hash) {
  * @param {Function} callback
  */
 
-ChainDB.prototype.reset = spawn.co(function* reset(block) {
+ChainDB.prototype.reset = co(function* reset(block) {
   var entry = yield this.get(block);
   var tip;
 
@@ -790,7 +791,7 @@ ChainDB.prototype.reset = spawn.co(function* reset(block) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-ChainDB.prototype.has = spawn.co(function* has(height) {
+ChainDB.prototype.has = co(function* has(height) {
   var items, hash;
 
   checkHash(height);
@@ -809,7 +810,7 @@ ChainDB.prototype.has = spawn.co(function* has(height) {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.saveBlock = spawn.co(function* saveBlock(block, view, connect) {
+ChainDB.prototype.saveBlock = co(function* saveBlock(block, view, connect) {
   if (this.options.spv)
     return block;
 
@@ -830,7 +831,7 @@ ChainDB.prototype.saveBlock = spawn.co(function* saveBlock(block, view, connect)
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.removeBlock = spawn.co(function* removeBlock(hash) {
+ChainDB.prototype.removeBlock = co(function* removeBlock(hash) {
   var block = yield this.getBlock(hash);
 
   if (!block)
@@ -847,7 +848,7 @@ ChainDB.prototype.removeBlock = spawn.co(function* removeBlock(hash) {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.connectBlock = spawn.co(function* connectBlock(block, view) {
+ChainDB.prototype.connectBlock = co(function* connectBlock(block, view) {
   var undo = new BufferWriter();
   var i, j, tx, input, output, prev;
   var hashes, address, hash, coins, raw;
@@ -946,7 +947,7 @@ ChainDB.prototype.connectBlock = spawn.co(function* connectBlock(block, view) {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.disconnectBlock = spawn.co(function* disconnectBlock(block) {
+ChainDB.prototype.disconnectBlock = co(function* disconnectBlock(block) {
   var i, j, tx, input, output, prev, view;
   var hashes, address, hash, coins, raw;
 
@@ -1040,7 +1041,7 @@ ChainDB.prototype.disconnectBlock = spawn.co(function* disconnectBlock(block) {
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-ChainDB.prototype.fillCoins = spawn.co(function* fillCoins(tx) {
+ChainDB.prototype.fillCoins = co(function* fillCoins(tx) {
   var i, input, coin;
 
   if (tx.isCoinbase())
@@ -1067,7 +1068,7 @@ ChainDB.prototype.fillCoins = spawn.co(function* fillCoins(tx) {
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-ChainDB.prototype.fillHistory = spawn.co(function* fillHistory(tx) {
+ChainDB.prototype.fillHistory = co(function* fillHistory(tx) {
   var i, input, tx;
 
   if (!this.options.indexTX)
@@ -1098,7 +1099,7 @@ ChainDB.prototype.fillHistory = spawn.co(function* fillHistory(tx) {
  * @param {Function} callback - Returns [Error, {@link Coin}].
  */
 
-ChainDB.prototype.getCoin = spawn.co(function* getCoin(hash, index) {
+ChainDB.prototype.getCoin = co(function* getCoin(hash, index) {
   var self = this;
   var coins = this.coinCache.get(hash);
 
@@ -1117,7 +1118,7 @@ ChainDB.prototype.getCoin = spawn.co(function* getCoin(hash, index) {
  * @param {Function} callback - Returns [Error, {@link Coins}].
  */
 
-ChainDB.prototype.getCoins = spawn.co(function* getCoins(hash) {
+ChainDB.prototype.getCoins = co(function* getCoins(hash) {
   var self = this;
   var coins = this.coinCache.get(hash);
 
@@ -1138,7 +1139,7 @@ ChainDB.prototype.getCoins = spawn.co(function* getCoins(hash) {
  * @param {Function} callback
  */
 
-ChainDB.prototype.scan = spawn.co(function* scan(start, filter, iter) {
+ChainDB.prototype.scan = co(function* scan(start, filter, iter) {
   var total = 0;
   var i, j, entry, hashes, hash, tx, txs, block;
 
@@ -1224,7 +1225,7 @@ ChainDB.prototype.hasTX = function hasTX(hash) {
  * @param {Function} callback - Returns [Error, {@link Coin}[]].
  */
 
-ChainDB.prototype.getCoinsByAddress = spawn.co(function* getCoinsByAddress(addresses) {
+ChainDB.prototype.getCoinsByAddress = co(function* getCoinsByAddress(addresses) {
   var coins = [];
   var i, j, address, hash, keys, key, coin;
 
@@ -1283,7 +1284,7 @@ ChainDB.prototype.getEntries = function getEntries() {
  * @param {Function} callback - Returns [Error, {@link Hash}[]].
  */
 
-ChainDB.prototype.getHashesByAddress = spawn.co(function* getHashesByAddress(addresses) {
+ChainDB.prototype.getHashesByAddress = co(function* getHashesByAddress(addresses) {
   var hashes = {};
   var i, address, hash;
 
@@ -1316,7 +1317,7 @@ ChainDB.prototype.getHashesByAddress = spawn.co(function* getHashesByAddress(add
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-ChainDB.prototype.getTXByAddress = spawn.co(function* getTXByAddress(addresses) {
+ChainDB.prototype.getTXByAddress = co(function* getTXByAddress(addresses) {
   var txs = [];
   var i, hashes, hash, tx;
 
@@ -1344,7 +1345,7 @@ ChainDB.prototype.getTXByAddress = spawn.co(function* getTXByAddress(addresses)
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-ChainDB.prototype.getFullTX = spawn.co(function* getFullTX(hash) {
+ChainDB.prototype.getFullTX = co(function* getFullTX(hash) {
   var tx;
 
   if (!this.options.indexTX)
@@ -1366,7 +1367,7 @@ ChainDB.prototype.getFullTX = spawn.co(function* getFullTX(hash) {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.getFullBlock = spawn.co(function* getFullBlock(hash) {
+ChainDB.prototype.getFullBlock = co(function* getFullBlock(hash) {
   var block = yield this.getBlock(hash);
   var view;
 
@@ -1384,7 +1385,7 @@ ChainDB.prototype.getFullBlock = spawn.co(function* getFullBlock(hash) {
  * @param {Function} callback - Returns [Error, {@link CoinView}].
  */
 
-ChainDB.prototype.getCoinView = spawn.co(function* getCoinView(block, callback) {
+ChainDB.prototype.getCoinView = co(function* getCoinView(block, callback) {
   var view = new bcoin.coinview();
   var prevout = block.getPrevout();
   var i, prev, coins;
@@ -1425,7 +1426,7 @@ ChainDB.prototype.getUndoCoins = function getUndoCoins(hash) {
  * @param {Function} callback - Returns [Error, {@link CoinView}].
  */
 
-ChainDB.prototype.getUndoView = spawn.co(function* getUndoView(block) {
+ChainDB.prototype.getUndoView = co(function* getUndoView(block) {
   var i, j, k, tx, input, coin, view, coins;
 
   view = yield this.getCoinView(block);
@@ -1459,7 +1460,7 @@ ChainDB.prototype.getUndoView = spawn.co(function* getUndoView(block) {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-ChainDB.prototype.getBlock = spawn.co(function* getBlock(hash) {
+ChainDB.prototype.getBlock = co(function* getBlock(hash) {
   var items = yield this.getBoth(hash);
   var height;
 
@@ -1495,7 +1496,7 @@ ChainDB.prototype.hasCoins = function hasCoins(hash) {
  * @param {Function} callback
  */
 
-ChainDB.prototype.pruneBlock = spawn.co(function* pruneBlock(block) {
+ChainDB.prototype.pruneBlock = co(function* pruneBlock(block) {
   var futureHeight, key, hash;
 
   if (this.options.spv)
diff --git a/lib/chain/chainentry.js b/lib/chain/chainentry.js
index d1d3bea3..03b93927 100644
--- a/lib/chain/chainentry.js
+++ b/lib/chain/chainentry.js
@@ -16,6 +16,7 @@ var assert = utils.assert;
 var BufferWriter = require('../utils/writer');
 var BufferReader = require('../utils/reader');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 
 /**
  * Represents an entry in the chain. Unlike
@@ -177,7 +178,7 @@ ChainEntry.prototype.getRetargetAncestors = function getRetargetAncestors() {
  * @param {Function} callback - Returns [Error, ChainEntry[]].
  */
 
-ChainEntry.prototype.getAncestors = spawn.co(function* getAncestors(max) {
+ChainEntry.prototype.getAncestors = co(function* getAncestors(max) {
   var entry = this;
   var ancestors = [];
   var cached;
@@ -230,7 +231,7 @@ ChainEntry.prototype.isMainChain = function isMainChain() {
  * @param {Function} callback - Returns [Error, ChainEntry[]].
  */
 
-ChainEntry.prototype.getAncestorByHeight = spawn.co(function* getAncestorByHeight(height) {
+ChainEntry.prototype.getAncestorByHeight = co(function* getAncestorByHeight(height) {
   var main, entry;
 
   if (height < 0)
@@ -262,7 +263,7 @@ ChainEntry.prototype.getAncestorByHeight = spawn.co(function* getAncestorByHeigh
  * @returns {Function} callback - Returns [Error, ChainEntry].
  */
 
-ChainEntry.prototype.getAncestor = spawn.co(function* getAncestor(index) {
+ChainEntry.prototype.getAncestor = co(function* getAncestor(index) {
   var ancestors;
 
   assert(index >= 0);
@@ -289,7 +290,7 @@ ChainEntry.prototype.getPrevious = function getPrevious() {
  * @param {Function} callback - Returns [Error, ChainEntry].
  */
 
-ChainEntry.prototype.getNext = spawn.co(function* getNext() {
+ChainEntry.prototype.getNext = co(function* getNext() {
   var hash = yield this.chain.db.getNextHash(this.hash);
   if (!hash)
     return;
@@ -322,7 +323,7 @@ ChainEntry.prototype.getMedianTime = function getMedianTime(ancestors) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-ChainEntry.prototype.getMedianTimeAsync = spawn.co(function* getMedianTimeAsync() {
+ChainEntry.prototype.getMedianTimeAsync = co(function* getMedianTimeAsync() {
   var MEDIAN_TIMESPAN = constants.block.MEDIAN_TIMESPAN;
   var ancestors = yield this.getAncestors(MEDIAN_TIMESPAN);
   return this.getMedianTime(ancestors);
@@ -409,7 +410,7 @@ ChainEntry.prototype.isSuperMajority = function isSuperMajority(version, require
  * @returns {Boolean}
  */
 
-ChainEntry.prototype.isSuperMajorityAsync = spawn.co(function* isSuperMajorityAsync(version, required) {
+ChainEntry.prototype.isSuperMajorityAsync = co(function* isSuperMajorityAsync(version, required) {
   var majorityWindow = this.network.block.majorityWindow;
   var ancestors = yield this.getAncestors(majorityWindow);
   return this.isSuperMajority(version, required, ancestors);
diff --git a/lib/crypto/crypto.js b/lib/crypto/crypto.js
index 073ecb22..c9025713 100644
--- a/lib/crypto/crypto.js
+++ b/lib/crypto/crypto.js
@@ -13,6 +13,7 @@ var scrypt = require('./scrypt');
 var scryptAsync = require('./scrypt-async');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var native = require('../utils/native');
 var nativeCrypto, hash, aes;
 
diff --git a/lib/db/lowlevelup.js b/lib/db/lowlevelup.js
index 072a9d50..1f5a5ec1 100644
--- a/lib/db/lowlevelup.js
+++ b/lib/db/lowlevelup.js
@@ -11,6 +11,7 @@ var utils = require('../utils/utils');
 var assert = utils.assert;
 var AsyncObject = require('../utils/async');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var P = utils.P;
 var VERSION_ERROR;
 
@@ -290,7 +291,7 @@ LowlevelUp.prototype.approximateSize = function approximateSize(start, end) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-LowlevelUp.prototype.has = spawn.co(function* has(key) {
+LowlevelUp.prototype.has = co(function* has(key) {
   var value = yield this.get(key);
   return value != null;
 });
@@ -303,7 +304,7 @@ LowlevelUp.prototype.has = spawn.co(function* has(key) {
  * @param {Function} callback - Returns [Error, Object].
  */
 
-LowlevelUp.prototype.fetch = spawn.co(function* fetch(key, parse) {
+LowlevelUp.prototype.fetch = co(function* fetch(key, parse) {
   var value = yield this.get(key);
   if (!value)
     return;
@@ -317,7 +318,7 @@ LowlevelUp.prototype.fetch = spawn.co(function* fetch(key, parse) {
  * @param {Function} callback - Returns [Error, Array].
  */
 
-LowlevelUp.prototype.iterate = spawn.co(function* iterate(options) {
+LowlevelUp.prototype.iterate = co(function* iterate(options) {
   var items = [];
   var iter, kv, result;
 
@@ -345,7 +346,7 @@ LowlevelUp.prototype.iterate = spawn.co(function* iterate(options) {
  * @param {Function} callback
  */
 
-LowlevelUp.prototype.checkVersion = spawn.co(function* checkVersion(key, version) {
+LowlevelUp.prototype.checkVersion = co(function* checkVersion(key, version) {
   var data = yield this.get(key);
 
   if (!data) {
@@ -367,7 +368,7 @@ LowlevelUp.prototype.checkVersion = spawn.co(function* checkVersion(key, version
  * @param {Function} callback
  */
 
-LowlevelUp.prototype.clone = spawn.co(function* clone(path) {
+LowlevelUp.prototype.clone = co(function* clone(path) {
   var opt = { keys: true, values: true };
   var options = utils.merge({}, this.options);
   var hwm = 256 << 20;
diff --git a/lib/http/client.js b/lib/http/client.js
index 9b435d25..2bbfcf89 100644
--- a/lib/http/client.js
+++ b/lib/http/client.js
@@ -12,6 +12,7 @@ var AsyncObject = require('../utils/async');
 var RPCClient = require('./rpcclient');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var request = require('./request').promise;
 
@@ -56,7 +57,7 @@ utils.inherits(HTTPClient, AsyncObject);
  * @param {Function} callback
  */
 
-HTTPClient.prototype._open = spawn.co(function* _open() {
+HTTPClient.prototype._open = co(function* _open() {
   var self = this;
   var IOClient;
 
@@ -163,7 +164,7 @@ HTTPClient.prototype._close = function close() {
  * @param {Function} callback - Returns [Error, Object?].
  */
 
-HTTPClient.prototype._request = spawn.co(function* _request(method, endpoint, json) {
+HTTPClient.prototype._request = co(function* _request(method, endpoint, json) {
   var query, network, height, res;
 
   if (this.token) {
@@ -565,7 +566,7 @@ HTTPClient.prototype.send = function send(id, options) {
  * @param {Function} callback
  */
 
-HTTPClient.prototype.retoken = spawn.co(function* retoken(id, passphrase) {
+HTTPClient.prototype.retoken = co(function* retoken(id, passphrase) {
   var options = { passphrase: passphrase };
   var body = yield this._post('/wallet/' + id + '/retoken', options);
   return body.token;
diff --git a/lib/http/rpc.js b/lib/http/rpc.js
index cd4355c5..b5ccc9f3 100644
--- a/lib/http/rpc.js
+++ b/lib/http/rpc.js
@@ -9,6 +9,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var crypto = require('../crypto/crypto');
 var assert = utils.assert;
 var constants = bcoin.constants;
@@ -293,7 +294,7 @@ RPC.prototype.execute = function execute(json) {
  * Overall control/query calls
  */
 
-RPC.prototype.getinfo = spawn.co(function* getinfo(args) {
+RPC.prototype.getinfo = co(function* getinfo(args) {
   var balance;
 
   if (args.help || args.length !== 0)
@@ -615,7 +616,7 @@ RPC.prototype._getSoftforks = function _getSoftforks() {
   ];
 };
 
-RPC.prototype._getBIP9Softforks = spawn.co(function* _getBIP9Softforks() {
+RPC.prototype._getBIP9Softforks = co(function* _getBIP9Softforks() {
   var forks = {};
   var keys = Object.keys(this.network.deployments);
   var i, id, deployment, state;
@@ -655,7 +656,7 @@ RPC.prototype._getBIP9Softforks = spawn.co(function* _getBIP9Softforks() {
 });
 
 /* Block chain and UTXO */
-RPC.prototype.getblockchaininfo = spawn.co(function* getblockchaininfo(args) {
+RPC.prototype.getblockchaininfo = co(function* getblockchaininfo(args) {
   if (args.help || args.length !== 0)
     throw new RPCError('getblockchaininfo');
 
@@ -716,7 +717,7 @@ RPC.prototype.getblockcount = function getblockcount(args) {
   return Promise.resolve(this.chain.tip.height);
 };
 
-RPC.prototype.getblock = spawn.co(function* getblock(args) {
+RPC.prototype.getblock = co(function* getblock(args) {
   var hash, verbose, entry, block;
 
   if (args.help || args.length < 1 || args.length > 2)
@@ -819,7 +820,7 @@ RPC.prototype._scriptToJSON = function scriptToJSON(script, hex) {
   return out;
 };
 
-RPC.prototype.getblockhash = spawn.co(function* getblockhash(args) {
+RPC.prototype.getblockhash = co(function* getblockhash(args) {
   var height, entry;
 
   if (args.help || args.length !== 1)
@@ -838,7 +839,7 @@ RPC.prototype.getblockhash = spawn.co(function* getblockhash(args) {
   return entry.rhash;
 });
 
-RPC.prototype.getblockheader = spawn.co(function* getblockheader(args) {
+RPC.prototype.getblockheader = co(function* getblockheader(args) {
   var hash, verbose, entry;
 
   if (args.help || args.length < 1 || args.length > 2)
@@ -865,7 +866,7 @@ RPC.prototype.getblockheader = spawn.co(function* getblockheader(args) {
   return yield this._headerToJSON(entry);
 });
 
-RPC.prototype._headerToJSON = spawn.co(function* _headerToJSON(entry) {
+RPC.prototype._headerToJSON = co(function* _headerToJSON(entry) {
   var medianTime = yield entry.getMedianTimeAsync();
   var nextHash = yield this.chain.db.getNextHash(entry.hash);
 
@@ -887,7 +888,7 @@ RPC.prototype._headerToJSON = spawn.co(function* _headerToJSON(entry) {
   };
 });
 
-RPC.prototype._blockToJSON = spawn.co(function* _blockToJSON(entry, block, txDetails) {
+RPC.prototype._blockToJSON = co(function* _blockToJSON(entry, block, txDetails) {
   var self = this;
   var medianTime = yield entry.getMedianTimeAsync();
   var nextHash = yield this.chain.db.getNextHash(entry.hash);
@@ -918,7 +919,7 @@ RPC.prototype._blockToJSON = spawn.co(function* _blockToJSON(entry, block, txDet
   };
 });
 
-RPC.prototype.getchaintips = spawn.co(function* getchaintips(args) {
+RPC.prototype.getchaintips = co(function* getchaintips(args) {
   var i, tips, orphans, prevs, result;
   var orphan, entries, entry, main, fork;
 
@@ -964,7 +965,7 @@ RPC.prototype.getchaintips = spawn.co(function* getchaintips(args) {
   return result;
 });
 
-RPC.prototype._findFork = spawn.co(function* _findFork(entry) {
+RPC.prototype._findFork = co(function* _findFork(entry) {
   while (entry) {
     if (yield entry.isMainChain())
       return entry;
@@ -1147,7 +1148,7 @@ RPC.prototype._entryToJSON = function _entryToJSON(entry) {
   };
 };
 
-RPC.prototype.gettxout = spawn.co(function* gettxout(args) {
+RPC.prototype.gettxout = co(function* gettxout(args) {
   var hash, index, mempool, coin;
 
   if (args.help || args.length < 2 || args.length > 3)
@@ -1187,7 +1188,7 @@ RPC.prototype.gettxout = spawn.co(function* gettxout(args) {
   };
 });
 
-RPC.prototype.gettxoutproof = spawn.co(function* gettxoutproof(args) {
+RPC.prototype.gettxoutproof = co(function* gettxoutproof(args) {
   var uniq = {};
   var i, txids, block, hash, last, tx, coins;
 
@@ -1253,7 +1254,7 @@ RPC.prototype.gettxoutproof = spawn.co(function* gettxoutproof(args) {
   return block.toRaw().toString('hex');
 });
 
-RPC.prototype.verifytxoutproof = spawn.co(function* verifytxoutproof(args) {
+RPC.prototype.verifytxoutproof = co(function* verifytxoutproof(args) {
   var res = [];
   var i, block, hash, entry;
 
@@ -1313,7 +1314,7 @@ RPC.prototype.verifychain = function verifychain(args) {
  * Mining
  */
 
-RPC.prototype._submitwork = spawn.co(function* _submitwork(data) {
+RPC.prototype._submitwork = co(function* _submitwork(data) {
   var attempt = this.attempt;
   var block, header, cb, cur;
 
@@ -1370,7 +1371,7 @@ RPC.prototype._submitwork = spawn.co(function* _submitwork(data) {
   return true;
 });
 
-RPC.prototype._getwork = spawn.co(function* _getwork() {
+RPC.prototype._getwork = co(function* _getwork() {
   var attempt = yield this._getAttempt(true);
   var data, abbr;
 
@@ -1401,7 +1402,7 @@ RPC.prototype.getworklp = function getworklp(args) {
   });
 };
 
-RPC.prototype.getwork = spawn.co(function* getwork(args) {
+RPC.prototype.getwork = co(function* getwork(args) {
   var unlock = yield this.locker.lock();
   var data, result;
 
@@ -1439,7 +1440,7 @@ RPC.prototype.getwork = spawn.co(function* getwork(args) {
   return result;
 });
 
-RPC.prototype.submitblock = spawn.co(function* submitblock(args) {
+RPC.prototype.submitblock = co(function* submitblock(args) {
   var unlock = yield this.locker.lock();
   var block;
 
@@ -1453,7 +1454,7 @@ RPC.prototype.submitblock = spawn.co(function* submitblock(args) {
   return yield this._submitblock(block);
 });
 
-RPC.prototype._submitblock = spawn.co(function* submitblock(block) {
+RPC.prototype._submitblock = co(function* submitblock(block) {
   if (block.prevBlock !== this.chain.tip.hash)
     return 'rejected: inconclusive-not-best-prevblk';
 
@@ -1468,7 +1469,7 @@ RPC.prototype._submitblock = spawn.co(function* submitblock(block) {
   return null;
 });
 
-RPC.prototype.getblocktemplate = spawn.co(function* getblocktemplate(args) {
+RPC.prototype.getblocktemplate = co(function* getblocktemplate(args) {
   var mode = 'template';
   var version = -1;
   var coinbase = true;
@@ -1537,7 +1538,7 @@ RPC.prototype.getblocktemplate = spawn.co(function* getblocktemplate(args) {
   return yield this._tmpl(version, coinbase, rules);
 });
 
-RPC.prototype._tmpl = spawn.co(function* _tmpl(version, coinbase, rules) {
+RPC.prototype._tmpl = co(function* _tmpl(version, coinbase, rules) {
   var unlock = yield this.locker.lock();
   var txs = [];
   var txIndex = {};
@@ -1745,7 +1746,7 @@ RPC.prototype._bindChain = function _bindChain() {
   });
 };
 
-RPC.prototype._getAttempt = spawn.co(function* _getAttempt(update) {
+RPC.prototype._getAttempt = co(function* _getAttempt(update) {
   var attempt = this.attempt;
 
   this._bindChain();
@@ -1771,7 +1772,7 @@ RPC.prototype._totalTX = function _totalTX() {
   return this.mempool ? this.mempool.totalTX : 0;
 };
 
-RPC.prototype.getmininginfo = spawn.co(function* getmininginfo(args) {
+RPC.prototype.getmininginfo = co(function* getmininginfo(args) {
   var block, hashps;
 
   if (args.help || args.length !== 0)
@@ -1853,7 +1854,7 @@ RPC.prototype.prioritisetransaction = function prioritisetransaction(args) {
   return Promise.resolve(true);
 };
 
-RPC.prototype._hashps = spawn.co(function* _hashps(lookup, height) {
+RPC.prototype._hashps = co(function* _hashps(lookup, height) {
   var i, minTime, maxTime, pb0, time;
   var workDiff, timeDiff, ps, pb, entry;
 
@@ -1921,7 +1922,7 @@ RPC.prototype.setgenerate = function setgenerate(args) {
   return Promise.resolve(this.mining);
 };
 
-RPC.prototype.generate = spawn.co(function* generate(args) {
+RPC.prototype.generate = co(function* generate(args) {
   var unlock = yield this.locker.lock();
   var numblocks;
 
@@ -1935,7 +1936,7 @@ RPC.prototype.generate = spawn.co(function* generate(args) {
   return yield this._generate(numblocks);
 });
 
-RPC.prototype._generate = spawn.co(function* _generate(numblocks) {
+RPC.prototype._generate = co(function* _generate(numblocks) {
   var hashes = [];
   var i, block;
 
@@ -1948,7 +1949,7 @@ RPC.prototype._generate = spawn.co(function* _generate(numblocks) {
   return hashes;
 });
 
-RPC.prototype.generatetoaddress = spawn.co(function* generatetoaddress(args) {
+RPC.prototype.generatetoaddress = co(function* generatetoaddress(args) {
   var unlock = yield this.locker.lock();
   var numblocks, address, hashes;
 
@@ -2105,7 +2106,7 @@ RPC.prototype.decodescript = function decodescript(args) {
   return Promise.resolve(script);
 };
 
-RPC.prototype.getrawtransaction = spawn.co(function* getrawtransaction(args) {
+RPC.prototype.getrawtransaction = co(function* getrawtransaction(args) {
   var hash, verbose, json, tx;
 
   if (args.help || args.length < 1 || args.length > 2)
@@ -2153,7 +2154,7 @@ RPC.prototype.sendrawtransaction = function sendrawtransaction(args) {
   return tx.rhash;
 };
 
-RPC.prototype.signrawtransaction = spawn.co(function* signrawtransaction(args) {
+RPC.prototype.signrawtransaction = co(function* signrawtransaction(args) {
   var raw, p, txs, merged;
 
   if (args.help || args.length < 1 || args.length > 4) {
@@ -2189,7 +2190,7 @@ RPC.prototype._fillCoins = function _fillCoins(tx) {
   return this.node.fillCoins(tx);
 };
 
-RPC.prototype._signrawtransaction = spawn.co(function* signrawtransaction(merged, txs, args) {
+RPC.prototype._signrawtransaction = co(function* signrawtransaction(merged, txs, args) {
   var keys = [];
   var keyMap = {};
   var k, i, secret, key;
@@ -2298,7 +2299,7 @@ RPC.prototype._signrawtransaction = spawn.co(function* signrawtransaction(merged
   };
 });
 
-RPC.prototype.fundrawtransaction = spawn.co(function* fundrawtransaction(args) {
+RPC.prototype.fundrawtransaction = co(function* fundrawtransaction(args) {
   var tx, options, changeAddress, feeRate;
 
   if (args.help || args.length < 1 || args.length > 2)
@@ -2336,7 +2337,7 @@ RPC.prototype.fundrawtransaction = spawn.co(function* fundrawtransaction(args) {
   };
 });
 
-RPC.prototype._createRedeem = spawn.co(function* _createRedeem(args) {
+RPC.prototype._createRedeem = co(function* _createRedeem(args) {
   var i, m, n, keys, hash, script, key, ring;
 
   if (!utils.isNumber(args[0])
@@ -2387,7 +2388,7 @@ RPC.prototype._createRedeem = spawn.co(function* _createRedeem(args) {
 });
 
 /*
- * Utility spawn.co(function* s
+ * Utility co(function* s
  */
 
 RPC.prototype.createmultisig = function createmultisig(args) {
@@ -2437,7 +2438,7 @@ RPC.prototype.createwitnessaddress = function createwitnessaddress(args) {
   });
 };
 
-RPC.prototype.validateaddress = spawn.co(function* validateaddress(args) {
+RPC.prototype.validateaddress = co(function* validateaddress(args) {
   var b58, address, json, path;
 
   if (args.help || args.length !== 1)
@@ -2670,7 +2671,7 @@ RPC.prototype.setmocktime = function setmocktime(args) {
  * Wallet
  */
 
-RPC.prototype.resendwallettransactions = spawn.co(function* resendwallettransactions(args) {
+RPC.prototype.resendwallettransactions = co(function* resendwallettransactions(args) {
   var hashes = [];
   var i, tx, txs;
 
@@ -2703,7 +2704,7 @@ RPC.prototype.addwitnessaddress = function addwitnessaddress(args) {
   Promise.reject(new Error('Not implemented.'));
 };
 
-RPC.prototype.backupwallet = spawn.co(function* backupwallet(args) {
+RPC.prototype.backupwallet = co(function* backupwallet(args) {
   var dest;
 
   if (args.help || args.length !== 1)
@@ -2715,7 +2716,7 @@ RPC.prototype.backupwallet = spawn.co(function* backupwallet(args) {
   return null;
 });
 
-RPC.prototype.dumpprivkey = spawn.co(function* dumpprivkey(args) {
+RPC.prototype.dumpprivkey = co(function* dumpprivkey(args) {
   var hash, ring;
 
   if (args.help || args.length !== 1)
@@ -2737,7 +2738,7 @@ RPC.prototype.dumpprivkey = spawn.co(function* dumpprivkey(args) {
   return ring.toSecret();
 });
 
-RPC.prototype.dumpwallet = spawn.co(function* dumpwallet(args) {
+RPC.prototype.dumpwallet = co(function* dumpwallet(args) {
   var i, file, time, address, fmt, str, out, hash, hashes, ring;
 
   if (args.help || args.length !== 1)
@@ -2795,7 +2796,7 @@ RPC.prototype.dumpwallet = spawn.co(function* dumpwallet(args) {
   return out;
 });
 
-RPC.prototype.encryptwallet = spawn.co(function* encryptwallet(args) {
+RPC.prototype.encryptwallet = co(function* encryptwallet(args) {
   var passphrase;
 
   if (!this.wallet.master.encrypted && (args.help || args.help !== 1))
@@ -2814,7 +2815,7 @@ RPC.prototype.encryptwallet = spawn.co(function* encryptwallet(args) {
   return 'wallet encrypted; we do not need to stop!';
 });
 
-RPC.prototype.getaccountaddress = spawn.co(function* getaccountaddress(args) {
+RPC.prototype.getaccountaddress = co(function* getaccountaddress(args) {
   var account;
 
   if (args.help || args.length !== 1)
@@ -2833,7 +2834,7 @@ RPC.prototype.getaccountaddress = spawn.co(function* getaccountaddress(args) {
   return account.receiveAddress.getAddress('base58');
 });
 
-RPC.prototype.getaccount = spawn.co(function* getaccount(args) {
+RPC.prototype.getaccount = co(function* getaccount(args) {
   var hash, path;
 
   if (args.help || args.length !== 1)
@@ -2852,7 +2853,7 @@ RPC.prototype.getaccount = spawn.co(function* getaccount(args) {
   return path.name;
 });
 
-RPC.prototype.getaddressesbyaccount = spawn.co(function* getaddressesbyaccount(args) {
+RPC.prototype.getaddressesbyaccount = co(function* getaddressesbyaccount(args) {
   var i, path, account, addrs, paths;
 
   if (args.help || args.length !== 1)
@@ -2875,7 +2876,7 @@ RPC.prototype.getaddressesbyaccount = spawn.co(function* getaddressesbyaccount(a
   return addrs;
 });
 
-RPC.prototype.getbalance = spawn.co(function* getbalance(args) {
+RPC.prototype.getbalance = co(function* getbalance(args) {
   var minconf = 0;
   var account, value, balance;
 
@@ -2903,7 +2904,7 @@ RPC.prototype.getbalance = spawn.co(function* getbalance(args) {
   return +utils.btc(value);
 });
 
-RPC.prototype.getnewaddress = spawn.co(function* getnewaddress(args) {
+RPC.prototype.getnewaddress = co(function* getnewaddress(args) {
   var account, address;
 
   if (args.help || args.length > 1)
@@ -2920,7 +2921,7 @@ RPC.prototype.getnewaddress = spawn.co(function* getnewaddress(args) {
   return address.getAddress('base58');
 });
 
-RPC.prototype.getrawchangeaddress = spawn.co(function* getrawchangeaddress(args) {
+RPC.prototype.getrawchangeaddress = co(function* getrawchangeaddress(args) {
   var address;
 
   if (args.help || args.length > 1)
@@ -2931,7 +2932,7 @@ RPC.prototype.getrawchangeaddress = spawn.co(function* getrawchangeaddress(args)
   return address.getAddress('base58');
 });
 
-RPC.prototype.getreceivedbyaccount = spawn.co(function* getreceivedbyaccount(args) {
+RPC.prototype.getreceivedbyaccount = co(function* getreceivedbyaccount(args) {
   var minconf = 0;
   var total = 0;
   var filter = {};
@@ -2984,7 +2985,7 @@ RPC.prototype.getreceivedbyaccount = spawn.co(function* getreceivedbyaccount(arg
   return +utils.btc(total);
 });
 
-RPC.prototype.getreceivedbyaddress = spawn.co(function* getreceivedbyaddress(args) {
+RPC.prototype.getreceivedbyaddress = co(function* getreceivedbyaddress(args) {
   var self = this;
   var minconf = 0;
   var total = 0;
@@ -3021,7 +3022,7 @@ RPC.prototype.getreceivedbyaddress = spawn.co(function* getreceivedbyaddress(arg
   return +utils.btc(total);
 });
 
-RPC.prototype._toWalletTX = spawn.co(function* _toWalletTX(tx) {
+RPC.prototype._toWalletTX = co(function* _toWalletTX(tx) {
   var i, det, receive, member, sent, received, json, details;
 
   details = yield this.wallet.toDetails(tx);
@@ -3098,7 +3099,7 @@ RPC.prototype._toWalletTX = spawn.co(function* _toWalletTX(tx) {
   return json;
 });
 
-RPC.prototype.gettransaction = spawn.co(function* gettransaction(args) {
+RPC.prototype.gettransaction = co(function* gettransaction(args) {
   var hash, tx;
 
   if (args.help || args.length < 1 || args.length > 2)
@@ -3117,7 +3118,7 @@ RPC.prototype.gettransaction = spawn.co(function* gettransaction(args) {
   return yield this._toWalletTX(tx);
 });
 
-RPC.prototype.abandontransaction = spawn.co(function* abandontransaction(args) {
+RPC.prototype.abandontransaction = co(function* abandontransaction(args) {
   var hash, result;
 
   if (args.help || args.length !== 1)
@@ -3136,7 +3137,7 @@ RPC.prototype.abandontransaction = spawn.co(function* abandontransaction(args) {
   return null;
 });
 
-RPC.prototype.getunconfirmedbalance = spawn.co(function* getunconfirmedbalance(args) {
+RPC.prototype.getunconfirmedbalance = co(function* getunconfirmedbalance(args) {
   var balance;
 
   if (args.help || args.length > 0)
@@ -3147,7 +3148,7 @@ RPC.prototype.getunconfirmedbalance = spawn.co(function* getunconfirmedbalance(a
   return +utils.btc(balance.unconfirmed);
 });
 
-RPC.prototype.getwalletinfo = spawn.co(function* getwalletinfo(args) {
+RPC.prototype.getwalletinfo = co(function* getwalletinfo(args) {
   var balance, hashes;
 
   if (args.help || args.length !== 0)
@@ -3171,7 +3172,7 @@ RPC.prototype.getwalletinfo = spawn.co(function* getwalletinfo(args) {
   };
 });
 
-RPC.prototype.importprivkey = spawn.co(function* importprivkey(args) {
+RPC.prototype.importprivkey = co(function* importprivkey(args) {
   var secret, label, rescan, key;
 
   if (args.help || args.length < 1 || args.length > 3)
@@ -3200,7 +3201,7 @@ RPC.prototype.importprivkey = spawn.co(function* importprivkey(args) {
   return null;
 });
 
-RPC.prototype.importwallet = spawn.co(function* importwallet(args) {
+RPC.prototype.importwallet = co(function* importwallet(args) {
   var file, keys, lines, line, parts;
   var i, secret, time, label, addr;
   var data, key;
@@ -3260,7 +3261,7 @@ RPC.prototype.importaddress = function importaddress(args) {
   return Promise.reject(new Error('Not implemented.'));
 };
 
-RPC.prototype.importpubkey = spawn.co(function* importpubkey(args) {
+RPC.prototype.importpubkey = co(function* importpubkey(args) {
   var pubkey, label, rescan, key;
 
   if (args.help || args.length < 1 || args.length > 4)
@@ -3300,7 +3301,7 @@ RPC.prototype.keypoolrefill = function keypoolrefill(args) {
   return Promise.resolve(null);
 };
 
-RPC.prototype.listaccounts = spawn.co(function* listaccounts(args) {
+RPC.prototype.listaccounts = co(function* listaccounts(args) {
   var i, map, accounts, account, balance;
 
   if (args.help || args.length > 2)
@@ -3380,7 +3381,7 @@ RPC.prototype.listreceivedbyaddress = function listreceivedbyaddress(args) {
   return this._listReceived(minconf, includeEmpty, false);
 };
 
-RPC.prototype._listReceived = spawn.co(function* _listReceived(minconf, empty, account) {
+RPC.prototype._listReceived = co(function* _listReceived(minconf, empty, account) {
   var out = [];
   var result = [];
   var map = {};
@@ -3472,7 +3473,7 @@ RPC.prototype._listReceived = spawn.co(function* _listReceived(minconf, empty, a
   return result;
 });
 
-RPC.prototype.listsinceblock = spawn.co(function* listsinceblock(args) {
+RPC.prototype.listsinceblock = co(function* listsinceblock(args) {
   var block, conf, out, highest;
   var i, height, txs, tx, json;
 
@@ -3526,7 +3527,7 @@ RPC.prototype.listsinceblock = spawn.co(function* listsinceblock(args) {
   };
 });
 
-RPC.prototype._toListTX = spawn.co(function* _toListTX(tx) {
+RPC.prototype._toListTX = co(function* _toListTX(tx) {
   var i, receive, member, det, sent, received, index;
   var sendMember, recMember, sendIndex, recIndex, json;
   var details;
@@ -3604,7 +3605,7 @@ RPC.prototype._toListTX = spawn.co(function* _toListTX(tx) {
   return json;
 });
 
-RPC.prototype.listtransactions = spawn.co(function* listtransactions(args) {
+RPC.prototype.listtransactions = co(function* listtransactions(args) {
   var i, account, count, txs, tx, json;
 
   if (args.help || args.length > 4) {
@@ -3639,7 +3640,7 @@ RPC.prototype.listtransactions = spawn.co(function* listtransactions(args) {
   return txs;
 });
 
-RPC.prototype.listunspent = spawn.co(function* listunspent(args) {
+RPC.prototype.listunspent = co(function* listunspent(args) {
   var minDepth = 1;
   var maxDepth = 9999999;
   var out = [];
@@ -3771,7 +3772,7 @@ RPC.prototype.move = function move(args) {
   Promise.reject(new Error('Not implemented.'));
 };
 
-RPC.prototype._send = spawn.co(function* _send(account, address, amount, subtractFee) {
+RPC.prototype._send = co(function* _send(account, address, amount, subtractFee) {
   var tx, options;
 
   options = {
@@ -3808,7 +3809,7 @@ RPC.prototype.sendfrom = function sendfrom(args) {
   return this._send(account, address, amount, false);
 };
 
-RPC.prototype.sendmany = spawn.co(function* sendmany(args) {
+RPC.prototype.sendmany = co(function* sendmany(args) {
   var account, sendTo, minDepth, comment, subtractFee;
   var i, outputs, keys, uniq, tx;
   var key, value, address, hash, output, options;
@@ -3906,7 +3907,7 @@ RPC.prototype.settxfee = function settxfee(args) {
   return Promise.resolve(true);
 };
 
-RPC.prototype.signmessage = spawn.co(function* signmessage(args) {
+RPC.prototype.signmessage = co(function* signmessage(args) {
   var address, msg, sig, ring;
 
   if (args.help || args.length !== 2)
@@ -3948,7 +3949,7 @@ RPC.prototype.walletlock = function walletlock(args) {
   return null;
 };
 
-RPC.prototype.walletpassphrasechange = spawn.co(function* walletpassphrasechange(args) {
+RPC.prototype.walletpassphrasechange = co(function* walletpassphrasechange(args) {
   var old, new_;
 
   if (args.help || (this.wallet.master.encrypted && args.length !== 2)) {
@@ -3970,7 +3971,7 @@ RPC.prototype.walletpassphrasechange = spawn.co(function* walletpassphrasechange
   return null;
 });
 
-RPC.prototype.walletpassphrase = spawn.co(function* walletpassphrase(args) {
+RPC.prototype.walletpassphrase = co(function* walletpassphrase(args) {
   var passphrase, timeout;
 
   if (args.help || (this.wallet.master.encrypted && args.length !== 2))
@@ -3993,7 +3994,7 @@ RPC.prototype.walletpassphrase = spawn.co(function* walletpassphrase(args) {
   return null;
 });
 
-RPC.prototype.importprunedfunds = spawn.co(function* importprunedfunds(args) {
+RPC.prototype.importprunedfunds = co(function* importprunedfunds(args) {
   var tx, block, label, height, added;
 
   if (args.help || args.length < 2 || args.length > 3) {
@@ -4037,7 +4038,7 @@ RPC.prototype.importprunedfunds = spawn.co(function* importprunedfunds(args) {
   return null;
 });
 
-RPC.prototype.removeprunedfunds = spawn.co(function* removeprunedfunds(args) {
+RPC.prototype.removeprunedfunds = co(function* removeprunedfunds(args) {
   var hash, removed;
 
   if (args.help || args.length !== 1)
diff --git a/lib/http/rpcclient.js b/lib/http/rpcclient.js
index a0d90e02..e2782dd2 100644
--- a/lib/http/rpcclient.js
+++ b/lib/http/rpcclient.js
@@ -9,6 +9,7 @@
 var Network = require('../protocol/network');
 var request = require('./request');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 
 /**
  * BCoin RPC client.
@@ -44,7 +45,7 @@ function RPCClient(options) {
  * @param {Function} callback - Returns [Error, Object?].
  */
 
-RPCClient.prototype.call = spawn.co(function* call(method, params) {
+RPCClient.prototype.call = co(function* call(method, params) {
   var res = yield request.promise({
     method: 'POST',
     uri: this.uri,
diff --git a/lib/http/server.js b/lib/http/server.js
index 80e0150b..efcfa9b7 100644
--- a/lib/http/server.js
+++ b/lib/http/server.js
@@ -16,6 +16,7 @@ var http = require('./');
 var HTTPBase = http.base;
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var crypto = require('../crypto/crypto');
 var assert = utils.assert;
 var RPC; /*= require('./rpc'); - load lazily */
@@ -1062,7 +1063,7 @@ HTTPServer.prototype._initIO = function _initIO() {
  * @param {Function} callback
  */
 
-HTTPServer.prototype.open = spawn.co(function* open() {
+HTTPServer.prototype.open = co(function* open() {
   yield this.server.open();
 
   this.logger.info('HTTP server loaded.');
diff --git a/lib/http/wallet.js b/lib/http/wallet.js
index 3292cb6b..d0d1c58f 100644
--- a/lib/http/wallet.js
+++ b/lib/http/wallet.js
@@ -12,6 +12,7 @@ var EventEmitter = require('events').EventEmitter;
 
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var Client = require('./client');
 
 /**
@@ -89,7 +90,7 @@ HTTPWallet.prototype._init = function _init() {
  * @param {Function} callback
  */
 
-HTTPWallet.prototype.open = spawn.co(function* open(options) {
+HTTPWallet.prototype.open = co(function* open(options) {
   var wallet;
 
   this.id = options.id;
@@ -116,7 +117,7 @@ HTTPWallet.prototype.open = spawn.co(function* open(options) {
  * @param {Function} callback
  */
 
-HTTPWallet.prototype.create = spawn.co(function* create(options) {
+HTTPWallet.prototype.create = co(function* create(options) {
   var wallet;
   yield this.client.open();
   wallet = yield this.client.createWallet(options);
@@ -292,7 +293,7 @@ HTTPWallet.prototype.setPassphrase = function setPassphrase(old, new_) {
  * @see Wallet#retoken
  */
 
-HTTPWallet.prototype.retoken = spawn.co(function* retoken(passphrase) {
+HTTPWallet.prototype.retoken = co(function* retoken(passphrase) {
   var token = yield this.client.retoken(this.id, passphrase);
 
   this.token = token;
diff --git a/lib/mempool/mempool.js b/lib/mempool/mempool.js
index 62280f74..689de518 100644
--- a/lib/mempool/mempool.js
+++ b/lib/mempool/mempool.js
@@ -12,6 +12,7 @@ var AsyncObject = require('../utils/async');
 var constants = bcoin.constants;
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var BufferWriter = require('../utils/writer');
 var BufferReader = require('../utils/reader');
@@ -119,7 +120,7 @@ utils.inherits(Mempool, AsyncObject);
  * @param {Function} callback
  */
 
-Mempool.prototype._open = spawn.co(function* open() {
+Mempool.prototype._open = co(function* open() {
   var size = (this.maxSize / 1024).toFixed(2);
   yield this.chain.open();
   this.logger.info('Mempool loaded (maxsize=%dkb).', size);
@@ -153,7 +154,7 @@ Mempool.prototype._lock = function _lock(tx, force) {
  * @param {Function} callback
  */
 
-Mempool.prototype.addBlock = spawn.co(function* addBlock(block) {
+Mempool.prototype.addBlock = co(function* addBlock(block) {
   var unlock = yield this._lock();
   var entries = [];
   var i, entry, tx, hash;
@@ -199,7 +200,7 @@ Mempool.prototype.addBlock = spawn.co(function* addBlock(block) {
  * @param {Function} callback
  */
 
-Mempool.prototype.removeBlock = spawn.co(function* removeBlock(block) {
+Mempool.prototype.removeBlock = co(function* removeBlock(block) {
   var unlock = yield this.lock();
   var i, entry, tx, hash;
 
@@ -524,7 +525,7 @@ Mempool.prototype.hasReject = function hasReject(hash) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Mempool.prototype.addTX = spawn.co(function* addTX(tx) {
+Mempool.prototype.addTX = co(function* addTX(tx) {
   var unlock = yield this._lock(tx);
   var missing;
 
@@ -550,7 +551,7 @@ Mempool.prototype.addTX = spawn.co(function* addTX(tx) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Mempool.prototype._addTX = spawn.co(function* _addTX(tx) {
+Mempool.prototype._addTX = co(function* _addTX(tx) {
   var lockFlags = constants.flags.STANDARD_LOCKTIME_FLAGS;
   var hash = tx.hash('hex');
   var ret, entry, missing;
@@ -670,7 +671,7 @@ Mempool.prototype._addTX = spawn.co(function* _addTX(tx) {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Mempool.prototype.addUnchecked = spawn.co(function* addUnchecked(entry, force) {
+Mempool.prototype.addUnchecked = co(function* addUnchecked(entry, force) {
   var unlock = yield this._lock(null, force);
   var i, resolved, tx, orphan;
 
@@ -804,7 +805,7 @@ Mempool.prototype.getMinRate = function getMinRate() {
  * @param {Function} callback - Returns [{@link VerifyError}].
  */
 
-Mempool.prototype.verify = spawn.co(function* verify(entry) {
+Mempool.prototype.verify = co(function* verify(entry) {
   var height = this.chain.height + 1;
   var lockFlags = flags.STANDARD_LOCKTIME_FLAGS;
   var flags1 = flags.STANDARD_VERIFY_FLAGS;
@@ -960,7 +961,7 @@ Mempool.prototype.verify = spawn.co(function* verify(entry) {
  * @param {Function} callback
  */
 
-Mempool.prototype.checkResult = spawn.co(function* checkResult(tx, flags) {
+Mempool.prototype.checkResult = co(function* checkResult(tx, flags) {
   try {
     yield this.checkInputs(tx, flags);
   } catch (err) {
@@ -979,7 +980,7 @@ Mempool.prototype.checkResult = spawn.co(function* checkResult(tx, flags) {
  * @param {Function} callback
  */
 
-Mempool.prototype.checkInputs = spawn.co(function* checkInputs(tx, flags) {
+Mempool.prototype.checkInputs = co(function* checkInputs(tx, flags) {
   var result = yield tx.verifyAsync(flags);
   if (result)
     return;
@@ -1387,7 +1388,7 @@ Mempool.prototype.fillAllHistory = function fillAllHistory(tx) {
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-Mempool.prototype.fillAllCoins = spawn.co(function* fillAllCoins(tx) {
+Mempool.prototype.fillAllCoins = co(function* fillAllCoins(tx) {
   var i, input, hash, index, coin;
 
   this.fillCoins(tx);
@@ -1463,7 +1464,7 @@ Mempool.prototype.isDoubleSpend = function isDoubleSpend(tx) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-Mempool.prototype.getConfidence = spawn.co(function* getConfidence(hash) {
+Mempool.prototype.getConfidence = co(function* getConfidence(hash) {
   var tx, result;
 
   if (hash instanceof bcoin.tx) {
diff --git a/lib/miner/miner.js b/lib/miner/miner.js
index 6b713ead..e65251ac 100644
--- a/lib/miner/miner.js
+++ b/lib/miner/miner.js
@@ -10,6 +10,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var AsyncObject = require('../utils/async');
 var MinerBlock = require('./minerblock');
@@ -134,7 +135,7 @@ Miner.prototype._init = function _init() {
  * @param {Function} callback
  */
 
-Miner.prototype._open = spawn.co(function* open() {
+Miner.prototype._open = co(function* open() {
   if (this.mempool)
     yield this.mempool.open();
   else
@@ -240,7 +241,7 @@ Miner.prototype.stop = function stop() {
  * @param {Function} callback - Returns [Error, {@link MinerBlock}].
  */
 
-Miner.prototype.createBlock = spawn.co(function* createBlock(tip) {
+Miner.prototype.createBlock = co(function* createBlock(tip) {
   var i, ts, attempt, txs, tx, target, version;
 
   if (!this.loaded)
@@ -294,7 +295,7 @@ Miner.prototype.createBlock = spawn.co(function* createBlock(tip) {
  * @param {Function} callback - Returns [Error, [{@link Block}]].
  */
 
-Miner.prototype.mineBlock = spawn.co(function* mineBlock(tip) {
+Miner.prototype.mineBlock = co(function* mineBlock(tip) {
 		// Create a new block and start hashing
 		var attempt = yield this.createBlock(tip);
   return yield attempt.mineAsync();
diff --git a/lib/miner/minerblock.js b/lib/miner/minerblock.js
index 04388551..2a0ca6c4 100644
--- a/lib/miner/minerblock.js
+++ b/lib/miner/minerblock.js
@@ -10,6 +10,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var crypto = require('../crypto/crypto');
 var assert = utils.assert;
 var constants = bcoin.constants;
@@ -349,7 +350,7 @@ MinerBlock.prototype.sendStatus = function sendStatus() {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-MinerBlock.prototype.mine = spawn.co(function* mine() {
+MinerBlock.prototype.mine = co(function* mine() {
   yield this.wait(100);
 
   // Try to find a block: do one iteration of extraNonce
@@ -391,7 +392,7 @@ MinerBlock.prototype.mineSync = function mineSync() {
  * @param {Function} callback - Returns [Error, {@link Block}].
  */
 
-MinerBlock.prototype.mineAsync = spawn.co(function* mineAsync() {
+MinerBlock.prototype.mineAsync = co(function* mineAsync() {
   var block;
 
   if (!this.workerPool)
diff --git a/lib/net/peer.js b/lib/net/peer.js
index 2e49f5a2..9e370230 100644
--- a/lib/net/peer.js
+++ b/lib/net/peer.js
@@ -11,6 +11,7 @@ var bcoin = require('../env');
 var EventEmitter = require('events').EventEmitter;
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var Parser = require('./parser');
 var Framer = require('./framer');
 var packets = require('./packets');
@@ -1430,7 +1431,7 @@ Peer.prototype._handleMempool = function _handleMempool(packet) {
  * [Error, {@link Block}|{@link MempoolEntry}].
  */
 
-Peer.prototype._getItem = spawn.co(function* _getItem(item) {
+Peer.prototype._getItem = co(function* _getItem(item) {
   var entry = this.pool.invMap[item.hash];
 
   if (entry) {
@@ -2349,7 +2350,7 @@ Peer.prototype.reject = function reject(obj, code, reason, score) {
  * @param {Function} callback
  */
 
-Peer.prototype.resolveOrphan = spawn.co(function* resolveOrphan(tip, orphan) {
+Peer.prototype.resolveOrphan = co(function* resolveOrphan(tip, orphan) {
   var root, locator;
 
   assert(orphan);
@@ -2373,7 +2374,7 @@ Peer.prototype.resolveOrphan = spawn.co(function* resolveOrphan(tip, orphan) {
  * @param {Function} callback
  */
 
-Peer.prototype.getHeaders = spawn.co(function* getHeaders(tip, stop) {
+Peer.prototype.getHeaders = co(function* getHeaders(tip, stop) {
   var locator = yield this.chain.getLocator(tip);
   this.sendGetHeaders(locator, stop);
 });
@@ -2385,7 +2386,7 @@ Peer.prototype.getHeaders = spawn.co(function* getHeaders(tip, stop) {
  * @param {Function} callback
  */
 
-Peer.prototype.getBlocks = spawn.co(function* getBlocks(tip, stop) {
+Peer.prototype.getBlocks = co(function* getBlocks(tip, stop) {
   var locator = yield this.chain.getLocator(tip);
   this.sendGetBlocks(locator, stop);
 });
diff --git a/lib/net/pool.js b/lib/net/pool.js
index e056bc84..f78a1315 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -13,6 +13,7 @@ var EventEmitter = require('events').EventEmitter;
 var utils = require('../utils/utils');
 var IP = require('../utils/ip');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var constants = bcoin.constants;
 var VerifyError = bcoin.errors.VerifyError;
@@ -290,7 +291,7 @@ Pool.prototype._lock = function _lock(force) {
  * @param {Function} callback
  */
 
-Pool.prototype._open = spawn.co(function* _open() {
+Pool.prototype._open = co(function* _open() {
   var ip, key;
 
   try {
@@ -329,7 +330,7 @@ Pool.prototype._open = spawn.co(function* _open() {
  * @param {Function} callback
  */
 
-Pool.prototype._close = spawn.co(function* close() {
+Pool.prototype._close = co(function* close() {
   var i, items, hashes, hash;
 
   this.stopSync();
@@ -720,7 +721,7 @@ Pool.prototype.stopSync = function stopSync() {
  * @param {Function} callback
  */
 
-Pool.prototype._handleHeaders = spawn.co(function* _handleHeaders(headers, peer) {
+Pool.prototype._handleHeaders = co(function* _handleHeaders(headers, peer) {
   var i, unlock, ret, header, hash, last;
 
   if (!this.options.headers)
@@ -789,7 +790,7 @@ Pool.prototype._handleHeaders = spawn.co(function* _handleHeaders(headers, peer)
  * @param {Function} callback
  */
 
-Pool.prototype._handleBlocks = spawn.co(function* _handleBlocks(hashes, peer) {
+Pool.prototype._handleBlocks = co(function* _handleBlocks(hashes, peer) {
   var i, hash, exists;
 
   assert(!this.options.headers);
@@ -857,7 +858,7 @@ Pool.prototype._handleBlocks = spawn.co(function* _handleBlocks(hashes, peer) {
  * @param {Function} callback
  */
 
-Pool.prototype._handleInv = spawn.co(function* _handleInv(hashes, peer) {
+Pool.prototype._handleInv = co(function* _handleInv(hashes, peer) {
   var unlock = yield this._lock();
   var i, hash;
 
@@ -888,7 +889,7 @@ Pool.prototype._handleInv = spawn.co(function* _handleInv(hashes, peer) {
  * @param {Function} callback
  */
 
-Pool.prototype._handleBlock = spawn.co(function* _handleBlock(block, peer) {
+Pool.prototype._handleBlock = co(function* _handleBlock(block, peer) {
   var requested;
 
   // Fulfill the load request.
@@ -1292,7 +1293,7 @@ Pool.prototype.hasReject = function hasReject(hash) {
  * @param {Function} callback
  */
 
-Pool.prototype._handleTX = spawn.co(function* _handleTX(tx, peer) {
+Pool.prototype._handleTX = co(function* _handleTX(tx, peer) {
   var i, requested, missing;
 
   // Fulfill the load request.
@@ -1503,7 +1504,7 @@ Pool.prototype.watchAddress = function watchAddress(address) {
  * @param {Function} callback
  */
 
-Pool.prototype.getData = spawn.co(function* getData(peer, type, hash) {
+Pool.prototype.getData = co(function* getData(peer, type, hash) {
   var self = this;
   var item, exists;
 
@@ -1565,7 +1566,7 @@ Pool.prototype.getDataSync = function getDataSync(peer, type, hash) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-Pool.prototype.has = spawn.co(function* has(peer, type, hash) {
+Pool.prototype.has = co(function* has(peer, type, hash) {
   var exists = yield this.exists(type, hash);
 
   if (exists)
@@ -1855,7 +1856,7 @@ Pool.prototype.isIgnored = function isIgnored(addr) {
  * @param {Function} callback
  */
 
-Pool.prototype.getIP = spawn.co(function* getIP() {
+Pool.prototype.getIP = co(function* getIP() {
   var request, res, ip;
 
   if (utils.isBrowser)
@@ -1887,7 +1888,7 @@ Pool.prototype.getIP = spawn.co(function* getIP() {
  * @param {Function} callback
  */
 
-Pool.prototype.getIP2 = spawn.co(function* getIP2() {
+Pool.prototype.getIP2 = co(function* getIP2() {
   var request, res, ip;
 
   if (utils.isBrowser)
diff --git a/lib/node/fullnode.js b/lib/node/fullnode.js
index d6a21ed6..62d0ab9c 100644
--- a/lib/node/fullnode.js
+++ b/lib/node/fullnode.js
@@ -11,6 +11,7 @@ var bcoin = require('../env');
 var constants = bcoin.constants;
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var Node = bcoin.node;
 
 /**
@@ -223,7 +224,7 @@ Fullnode.prototype._init = function _init() {
  * @param {Function} callback
  */
 
-Fullnode.prototype._open = spawn.co(function* open() {
+Fullnode.prototype._open = co(function* open() {
   yield this.chain.open();
   yield this.mempool.open();
   yield this.miner.open();
@@ -251,7 +252,7 @@ Fullnode.prototype._open = spawn.co(function* open() {
  * @param {Function} callback
  */
 
-Fullnode.prototype._close = spawn.co(function* close() {
+Fullnode.prototype._close = co(function* close() {
   this.wallet = null;
 
   if (this.http)
@@ -305,7 +306,7 @@ Fullnode.prototype.broadcast = function broadcast(item, callback) {
  * @param {TX} tx
  */
 
-Fullnode.prototype.sendTX = spawn.co(function* sendTX(tx) {
+Fullnode.prototype.sendTX = co(function* sendTX(tx) {
   try {
     yield this.mempool.addTX(tx);
   } catch (err) {
@@ -404,7 +405,7 @@ Fullnode.prototype.getCoin = function getCoin(hash, index) {
  * @param {Function} callback - Returns [Error, {@link Coin}[]].
  */
 
-Fullnode.prototype.getCoinsByAddress = spawn.co(function* getCoinsByAddress(addresses) {
+Fullnode.prototype.getCoinsByAddress = co(function* getCoinsByAddress(addresses) {
   var coins = this.mempool.getCoinsByAddress(addresses);
   var i, blockCoins, coin, spent;
 
@@ -428,7 +429,7 @@ Fullnode.prototype.getCoinsByAddress = spawn.co(function* getCoinsByAddress(addr
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-Fullnode.prototype.getTXByAddress = spawn.co(function* getTXByAddress(addresses) {
+Fullnode.prototype.getTXByAddress = co(function* getTXByAddress(addresses) {
   var mempool = this.mempool.getTXByAddress(addresses);
   var txs = yield this.chain.db.getTXByAddress(addresses);
   return mempool.concat(txs);
diff --git a/lib/node/node.js b/lib/node/node.js
index 7a9ec16b..beb8d49d 100644
--- a/lib/node/node.js
+++ b/lib/node/node.js
@@ -11,6 +11,7 @@ var bcoin = require('../env');
 var AsyncObject = require('../utils/async');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 
 /**
@@ -233,7 +234,7 @@ Node.prototype.location = function location(name) {
  * @param {Function} callback
  */
 
-Node.prototype.openWallet = spawn.co(function* openWallet() {
+Node.prototype.openWallet = co(function* openWallet() {
   var options, wallet;
 
   assert(!this.wallet);
diff --git a/lib/node/spvnode.js b/lib/node/spvnode.js
index 8d42ee96..f118c083 100644
--- a/lib/node/spvnode.js
+++ b/lib/node/spvnode.js
@@ -10,6 +10,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var Node = bcoin.node;
 
 /**
@@ -147,7 +148,7 @@ SPVNode.prototype._init = function _init() {
  * @param {Function} callback
  */
 
-SPVNode.prototype._open = spawn.co(function* open(callback) {
+SPVNode.prototype._open = co(function* open(callback) {
   yield this.chain.open();
   yield this.pool.open();
   yield this.walletdb.open();
@@ -176,7 +177,7 @@ SPVNode.prototype._open = spawn.co(function* open(callback) {
  * @param {Function} callback
  */
 
-SPVNode.prototype._close = spawn.co(function* close() {
+SPVNode.prototype._close = co(function* close() {
   this.wallet = null;
   if (this.http)
     yield this.http.close();
@@ -190,7 +191,7 @@ SPVNode.prototype._close = spawn.co(function* close() {
  * @param {Function} callback
  */
 
-SPVNode.prototype.openFilter = spawn.co(function* openFilter() {
+SPVNode.prototype.openFilter = co(function* openFilter() {
   var hashes = yield this.walletdb.getAddressHashes();
   var i;
 
diff --git a/lib/utils/async.js b/lib/utils/async.js
index 29087ed2..c9a88d39 100644
--- a/lib/utils/async.js
+++ b/lib/utils/async.js
@@ -8,6 +8,7 @@
 
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var EventEmitter = require('events').EventEmitter;
 var wait = utils.wait;
@@ -53,7 +54,7 @@ AsyncObject.prototype._onClose = function _onClose() {
   });
 };
 
-AsyncObject.prototype.open = spawn.co(function* open() {
+AsyncObject.prototype.open = co(function* open() {
   var err, unlock;
 
   assert(!this.closing, 'Cannot open while closing.');
@@ -100,7 +101,7 @@ AsyncObject.prototype.open = spawn.co(function* open() {
  * @param {Function} callback
  */
 
-AsyncObject.prototype.close = spawn.co(function* close() {
+AsyncObject.prototype.close = co(function* close() {
   var unlock, err;
 
   assert(!this.loading, 'Cannot close while loading.');
diff --git a/lib/wallet/account.js b/lib/wallet/account.js
index efedd974..754d06a9 100644
--- a/lib/wallet/account.js
+++ b/lib/wallet/account.js
@@ -9,6 +9,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = utils.assert;
 var BufferReader = require('../utils/reader');
 var BufferWriter = require('../utils/writer');
@@ -204,7 +205,7 @@ Account.MAX_LOOKAHEAD = 5;
  * @param {Function} callback
  */
 
-Account.prototype.init = spawn.co(function* init() {
+Account.prototype.init = co(function* init() {
   // Waiting for more keys.
   if (this.keys.length !== this.n - 1) {
     assert(!this.initialized);
@@ -304,7 +305,7 @@ Account.prototype.spliceKey = function spliceKey(key) {
  * @param {Function} callback
  */
 
-Account.prototype.addKey = spawn.co(function* addKey(key) {
+Account.prototype.addKey = co(function* addKey(key) {
   var result = false;
   var exists;
 
@@ -333,7 +334,7 @@ Account.prototype.addKey = spawn.co(function* addKey(key) {
  * @param {Function} callback
  */
 
-Account.prototype._checkKeys = spawn.co(function* _checkKeys() {
+Account.prototype._checkKeys = co(function* _checkKeys() {
   var ring, hash, paths;
 
   if (this.initialized || this.type !== Account.types.MULTISIG)
@@ -398,7 +399,7 @@ Account.prototype.createChange = function createChange() {
  * @param {Function} callback - Returns [Error, {@link KeyRing}].
  */
 
-Account.prototype.createAddress = spawn.co(function* createAddress(change) {
+Account.prototype.createAddress = co(function* createAddress(change) {
   var ring, lookahead;
 
   if (change) {
@@ -560,7 +561,7 @@ Account.prototype.saveAddress = function saveAddress(rings) {
  * @param {Function} callback - Returns [Error, {@link KeyRing}, {@link KeyRing}].
  */
 
-Account.prototype.setDepth = spawn.co(function* setDepth(receiveDepth, changeDepth) {
+Account.prototype.setDepth = co(function* setDepth(receiveDepth, changeDepth) {
   var rings = [];
   var i, receive, change;
 
diff --git a/lib/wallet/txdb.js b/lib/wallet/txdb.js
index e4e036dc..1a437f37 100644
--- a/lib/wallet/txdb.js
+++ b/lib/wallet/txdb.js
@@ -10,6 +10,7 @@
 var bcoin = require('../env');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var assert = bcoin.utils.assert;
 var constants = bcoin.constants;
 var DUMMY = new Buffer([0]);
@@ -229,7 +230,7 @@ TXDB.layout = layout;
  * @param {Function} callback
  */
 
-TXDB.prototype.open = spawn.co(function* open() {
+TXDB.prototype.open = co(function* open() {
   this.balance = yield this.getBalance();
   this.logger.info('TXDB loaded for %s.', this.wallet.id);
   this.logger.info(
@@ -372,7 +373,7 @@ TXDB.prototype.iterate = function iterate(options) {
  * @param {Function} callback
  */
 
-TXDB.prototype.commit = spawn.co(function* commit() {
+TXDB.prototype.commit = co(function* commit() {
   assert(this.current);
   try {
     yield this.current.write();
@@ -402,7 +403,7 @@ TXDB.prototype.getInfo = function getInfo(tx) {
  * @param {Function} callback - Returns [Error, Buffer].
  */
 
-TXDB.prototype._addOrphan = spawn.co(function* _addOrphan(prevout, spender) {
+TXDB.prototype._addOrphan = co(function* _addOrphan(prevout, spender) {
   var p = new BufferWriter();
   var key = layout.o(prevout.hash, prevout.index);
   var data = yield this.get(key);
@@ -423,7 +424,7 @@ TXDB.prototype._addOrphan = spawn.co(function* _addOrphan(prevout, spender) {
  * @param {Function} callback - Returns [Error, {@link Orphan}].
  */
 
-TXDB.prototype._getOrphans = spawn.co(function* _getOrphans(hash, index) {
+TXDB.prototype._getOrphans = co(function* _getOrphans(hash, index) {
   var items = [];
   var i, orphans, orphan, tx;
 
@@ -458,7 +459,7 @@ TXDB.prototype._getOrphans = spawn.co(function* _getOrphans(hash, index) {
  * @param {Function} callback - Returns [Error].
  */
 
-TXDB.prototype._verify = spawn.co(function* _verify(tx, info) {
+TXDB.prototype._verify = co(function* _verify(tx, info) {
   var i, input, prevout, address, coin, spent, rtx, rinfo, result;
 
   for (i = 0; i < tx.inputs.length; i++) {
@@ -539,7 +540,7 @@ TXDB.prototype._verify = spawn.co(function* _verify(tx, info) {
  * @param {Function} callback
  */
 
-TXDB.prototype._resolveOrphans = spawn.co(function* _resolveOrphans(tx, index) {
+TXDB.prototype._resolveOrphans = co(function* _resolveOrphans(tx, index) {
   var hash = tx.hash('hex');
   var i, orphans, coin, item, input, orphan;
 
@@ -592,7 +593,7 @@ TXDB.prototype._resolveOrphans = spawn.co(function* _resolveOrphans(tx, index) {
  * @param {Function} callback
  */
 
-TXDB.prototype.add = spawn.co(function* add(tx, info) {
+TXDB.prototype.add = co(function* add(tx, info) {
   var unlock = yield this._lock();
   var hash, path, account;
   var i, result, input, output, coin;
@@ -743,7 +744,7 @@ TXDB.prototype.add = spawn.co(function* add(tx, info) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-TXDB.prototype._removeConflict = spawn.co(function* _removeConflict(hash, ref) {
+TXDB.prototype._removeConflict = co(function* _removeConflict(hash, ref) {
   var tx = yield this.getTX(hash);
   var info;
 
@@ -785,7 +786,7 @@ TXDB.prototype._removeConflict = spawn.co(function* _removeConflict(hash, ref) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-TXDB.prototype._removeRecursive = spawn.co(function* _removeRecursive(tx) {
+TXDB.prototype._removeRecursive = co(function* _removeRecursive(tx) {
   var hash = tx.hash('hex');
   var i, spent, stx, info;
 
@@ -830,7 +831,7 @@ TXDB.prototype._removeRecursive = spawn.co(function* _removeRecursive(tx) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-TXDB.prototype.isDoubleSpend = spawn.co(function* isDoubleSpend(tx) {
+TXDB.prototype.isDoubleSpend = co(function* isDoubleSpend(tx) {
   var i, input, prevout, spent;
 
   for (i = 0; i < tx.inputs.length; i++) {
@@ -868,7 +869,7 @@ TXDB.prototype.isSpent = function isSpent(hash, index) {
  * transaction was confirmed, or should be ignored.
  */
 
-TXDB.prototype._confirm = spawn.co(function* _confirm(tx, info) {
+TXDB.prototype._confirm = co(function* _confirm(tx, info) {
   var hash = tx.hash('hex');
   var i, account, existing, output, coin;
   var address, key;
@@ -962,7 +963,7 @@ TXDB.prototype._confirm = spawn.co(function* _confirm(tx, info) {
  * @param {Function} callback - Returns [Error].
  */
 
-TXDB.prototype.remove = spawn.co(function* remove(hash, force) {
+TXDB.prototype.remove = co(function* remove(hash, force) {
   var unlock = yield this._lock(force);
   var info = yield this._removeRecursive();
 
@@ -982,7 +983,7 @@ TXDB.prototype.remove = spawn.co(function* remove(hash, force) {
  * @param {Function} callback - Returns [Error].
  */
 
-TXDB.prototype._lazyRemove = spawn.co(function* lazyRemove(tx) {
+TXDB.prototype._lazyRemove = co(function* lazyRemove(tx) {
   var info = yield this.getInfo(tx);
   if (!info)
     return;
@@ -998,7 +999,7 @@ TXDB.prototype._lazyRemove = spawn.co(function* lazyRemove(tx) {
  * @param {Function} callback - Returns [Error].
  */
 
-TXDB.prototype._remove = spawn.co(function* remove(tx, info) {
+TXDB.prototype._remove = co(function* remove(tx, info) {
   var hash = tx.hash('hex');
   var i, path, account, key, prevout;
   var address, input, output, coin;
@@ -1085,7 +1086,7 @@ TXDB.prototype._remove = spawn.co(function* remove(tx, info) {
  * @param {Function} callback
  */
 
-TXDB.prototype.unconfirm = spawn.co(function* unconfirm(hash, force) {
+TXDB.prototype.unconfirm = co(function* unconfirm(hash, force) {
   var unlock = yield this._lock(force);
   var tx, info, result;
 
@@ -1141,7 +1142,7 @@ TXDB.prototype.unconfirm = spawn.co(function* unconfirm(hash, force) {
  * @param {Function} callback
  */
 
-TXDB.prototype._unconfirm = spawn.co(function* unconfirm(tx, info) {
+TXDB.prototype._unconfirm = co(function* unconfirm(tx, info) {
   var hash = tx.hash('hex');
   var height = tx.height;
   var i, account, output, key, coin;
@@ -1475,7 +1476,7 @@ TXDB.prototype.getRangeHashes = function getRangeHashes(account, options) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-TXDB.prototype.getRange = spawn.co(function* getRange(account, options) {
+TXDB.prototype.getRange = co(function* getRange(account, options) {
   var txs = [];
   var i, hashes, hash, tx;
 
@@ -1544,7 +1545,7 @@ TXDB.prototype.getHistory = function getHistory(account) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-TXDB.prototype.getAccountHistory = spawn.co(function* getAccountHistory(account) {
+TXDB.prototype.getAccountHistory = co(function* getAccountHistory(account) {
   var txs = [];
   var i, hashes, hash, tx;
 
@@ -1569,7 +1570,7 @@ TXDB.prototype.getAccountHistory = spawn.co(function* getAccountHistory(account)
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-TXDB.prototype.getUnconfirmed = spawn.co(function* getUnconfirmed(account) {
+TXDB.prototype.getUnconfirmed = co(function* getUnconfirmed(account) {
   var txs = [];
   var i, hashes, hash, tx;
 
@@ -1626,7 +1627,7 @@ TXDB.prototype.getCoins = function getCoins(account) {
  * @param {Function} callback - Returns [Error, {@link Coin}[]].
  */
 
-TXDB.prototype.getAccountCoins = spawn.co(function* getCoins(account) {
+TXDB.prototype.getAccountCoins = co(function* getCoins(account) {
   var coins = [];
   var i, hashes, key, coin;
 
@@ -1678,7 +1679,7 @@ TXDB.prototype.fillHistory = function fillHistory(tx) {
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-TXDB.prototype.fillCoins = spawn.co(function* fillCoins(tx) {
+TXDB.prototype.fillCoins = co(function* fillCoins(tx) {
   var i, input, prevout, coin;
 
   if (tx.isCoinbase())
@@ -1718,7 +1719,7 @@ TXDB.prototype.getTX = function getTX(hash) {
  * @param {Function} callback - Returns [Error, {@link TXDetails}].
  */
 
-TXDB.prototype.getDetails = spawn.co(function* getDetails(hash) {
+TXDB.prototype.getDetails = co(function* getDetails(hash) {
   var tx = yield this.getTX(hash);
 
   if (!tx)
@@ -1733,7 +1734,7 @@ TXDB.prototype.getDetails = spawn.co(function* getDetails(hash) {
  * @param {Function} callback
  */
 
-TXDB.prototype.toDetails = spawn.co(function* toDetails(tx) {
+TXDB.prototype.toDetails = co(function* toDetails(tx) {
   var i, out, txs, details, info;
 
   if (Array.isArray(tx)) {
@@ -1828,7 +1829,7 @@ TXDB.prototype.getSpentCoin = function getSpentCoin(spent, prevout) {
  * @param {Function} callback
  */
 
-TXDB.prototype.updateSpentCoin = spawn.co(function* updateSpentCoin(tx, i) {
+TXDB.prototype.updateSpentCoin = co(function* updateSpentCoin(tx, i) {
   var prevout = bcoin.outpoint.fromTX(tx, i);
   var spent = yield this.isSpent(prevout.hash, prevout.index);
   var coin;
@@ -1867,7 +1868,7 @@ TXDB.prototype.hasCoin = function hasCoin(hash, index) {
  * @param {Function} callback - Returns [Error, {@link Balance}].
  */
 
-TXDB.prototype.getBalance = spawn.co(function* getBalance(account) {
+TXDB.prototype.getBalance = co(function* getBalance(account) {
   var self = this;
   var balance;
 
@@ -1905,7 +1906,7 @@ TXDB.prototype.getBalance = spawn.co(function* getBalance(account) {
  * @param {Function} callback - Returns [Error, {@link Balance}].
  */
 
-TXDB.prototype.getAccountBalance = spawn.co(function* getBalance(account) {
+TXDB.prototype.getAccountBalance = co(function* getBalance(account) {
   var balance = new Balance(this.wallet);
   var i, key, coin, hashes, hash, data;
 
@@ -1940,7 +1941,7 @@ TXDB.prototype.getAccountBalance = spawn.co(function* getBalance(account) {
  * @param {Function} callback
  */
 
-TXDB.prototype.zap = spawn.co(function* zap(account, age) {
+TXDB.prototype.zap = co(function* zap(account, age) {
   var unlock = yield this._lock();
   var i, txs, tx, hash;
 
@@ -1976,7 +1977,7 @@ TXDB.prototype.zap = spawn.co(function* zap(account, age) {
  * @param {Function} callback
  */
 
-TXDB.prototype.abandon = spawn.co(function* abandon(hash) {
+TXDB.prototype.abandon = co(function* abandon(hash) {
   var result = yield this.has(layout.p(hash));
   if (!result)
     throw new Error('TX not eligible.');
diff --git a/lib/wallet/wallet.js b/lib/wallet/wallet.js
index e6f63cc9..934e5ce9 100644
--- a/lib/wallet/wallet.js
+++ b/lib/wallet/wallet.js
@@ -12,6 +12,7 @@ var EventEmitter = require('events').EventEmitter;
 var constants = bcoin.constants;
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var crypto = require('../crypto/crypto');
 var assert = utils.assert;
 var BufferReader = require('../utils/reader');
@@ -179,7 +180,7 @@ Wallet.fromOptions = function fromOptions(db, options) {
  * @param {Function} callback
  */
 
-Wallet.prototype.init = spawn.co(function* init(options) {
+Wallet.prototype.init = co(function* init(options) {
   var account;
 
   assert(!this.initialized);
@@ -203,7 +204,7 @@ Wallet.prototype.init = spawn.co(function* init(options) {
  * @param {Function} callback
  */
 
-Wallet.prototype.open = spawn.co(function* open() {
+Wallet.prototype.open = co(function* open() {
   var account;
 
   assert(this.initialized);
@@ -244,7 +245,7 @@ Wallet.prototype.destroy = function destroy() {
  * @param {Function} callback
  */
 
-Wallet.prototype.addKey = spawn.co(function* addKey(account, key) {
+Wallet.prototype.addKey = co(function* addKey(account, key) {
   var unlock = yield this._lockWrite();
   var result;
 
@@ -286,7 +287,7 @@ Wallet.prototype.addKey = spawn.co(function* addKey(account, key) {
  * @param {Function} callback
  */
 
-Wallet.prototype.removeKey = spawn.co(function* removeKey(account, key) {
+Wallet.prototype.removeKey = co(function* removeKey(account, key) {
   var unlock = yield this._lockWrite();
   var result;
 
@@ -328,7 +329,7 @@ Wallet.prototype.removeKey = spawn.co(function* removeKey(account, key) {
  * @param {Function} callback
  */
 
-Wallet.prototype.setPassphrase = spawn.co(function* setPassphrase(old, new_) {
+Wallet.prototype.setPassphrase = co(function* setPassphrase(old, new_) {
   var unlock = yield this._lockWrite();
 
   if (!new_) {
@@ -358,7 +359,7 @@ Wallet.prototype.setPassphrase = spawn.co(function* setPassphrase(old, new_) {
  * @param {Function} callback
  */
 
-Wallet.prototype.retoken = spawn.co(function* retoken(passphrase) {
+Wallet.prototype.retoken = co(function* retoken(passphrase) {
   var unlock = yield this._lockWrite();
   var master;
 
@@ -459,7 +460,7 @@ Wallet.prototype.getToken = function getToken(master, nonce) {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-Wallet.prototype.createAccount = spawn.co(function* createAccount(options) {
+Wallet.prototype.createAccount = co(function* createAccount(options) {
   var unlock = yield this._lockWrite();
   var passphrase = options.passphrase;
   var timeout = options.timeout;
@@ -519,7 +520,7 @@ Wallet.prototype.createAccount = spawn.co(function* createAccount(options) {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-Wallet.prototype.ensureAccount = spawn.co(function* ensureAccount(options) {
+Wallet.prototype.ensureAccount = co(function* ensureAccount(options) {
   var account = options.account;
   var exists;
 
@@ -558,7 +559,7 @@ Wallet.prototype.getAddressHashes = function getAddressHashes() {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-Wallet.prototype.getAccount = spawn.co(function* getAccount(account) {
+Wallet.prototype.getAccount = co(function* getAccount(account) {
   if (this.account) {
     if (account === 0 || account === 'default')
       return this.account;
@@ -612,7 +613,7 @@ Wallet.prototype.createChange = function createChange(account) {
  * @param {Function} callback - Returns [Error, {@link KeyRing}].
  */
 
-Wallet.prototype.createAddress = spawn.co(function* createAddress(account, change) {
+Wallet.prototype.createAddress = co(function* createAddress(account, change) {
   var unlock = yield this._lockWrite();
   var result;
 
@@ -708,7 +709,7 @@ Wallet.prototype.hasAddress = function hasAddress(address) {
  * @param {Function} callback - Returns [Error, {@link Path}].
  */
 
-Wallet.prototype.getPath = spawn.co(function* getPath(address) {
+Wallet.prototype.getPath = co(function* getPath(address) {
   var hash = bcoin.address.getHash(address, 'hex');
   var path;
 
@@ -731,7 +732,7 @@ Wallet.prototype.getPath = spawn.co(function* getPath(address) {
  * @param {Function} callback - Returns [Error, {@link Path}].
  */
 
-Wallet.prototype.getPaths = spawn.co(function* getPaths(account) {
+Wallet.prototype.getPaths = co(function* getPaths(account) {
   var out = [];
   var i, account, paths, path;
 
@@ -758,7 +759,7 @@ Wallet.prototype.getPaths = spawn.co(function* getPaths(account) {
  * @param {Function} callback
  */
 
-Wallet.prototype.importKey = spawn.co(function* importKey(account, ring, passphrase) {
+Wallet.prototype.importKey = co(function* importKey(account, ring, passphrase) {
   var unlock = yield this._lockWrite();
   var exists, account, raw, path;
 
@@ -852,7 +853,7 @@ Wallet.prototype.importKey = spawn.co(function* importKey(account, ring, passphr
  * fee from existing outputs rather than adding more inputs.
  */
 
-Wallet.prototype.fund = spawn.co(function* fund(tx, options, force) {
+Wallet.prototype.fund = co(function* fund(tx, options, force) {
   var unlock = yield this._lockFund(force);
   var rate, account, coins;
 
@@ -924,7 +925,7 @@ Wallet.prototype.fund = spawn.co(function* fund(tx, options, force) {
  * @param {Function} callback - Returns [Error, {@link MTX}].
  */
 
-Wallet.prototype.createTX = spawn.co(function* createTX(options, force) {
+Wallet.prototype.createTX = co(function* createTX(options, force) {
   var outputs = options.outputs;
   var i, tx, total;
 
@@ -975,7 +976,7 @@ Wallet.prototype.createTX = spawn.co(function* createTX(options, force) {
  * @param {Function} callback - Returns [Error, {@link TX}].
  */
 
-Wallet.prototype.send = spawn.co(function* send(options) {
+Wallet.prototype.send = co(function* send(options) {
   var unlock = yield this._lockFund();
   var tx;
 
@@ -1014,7 +1015,7 @@ Wallet.prototype.send = spawn.co(function* send(options) {
  * @param {Function} callback
  */
 
-Wallet.prototype.resend = spawn.co(function* resend() {
+Wallet.prototype.resend = co(function* resend() {
   var txs = yield this.getUnconfirmed();
   var i;
 
@@ -1034,7 +1035,7 @@ Wallet.prototype.resend = spawn.co(function* resend() {
  * @param {Function} callback - Returns [Error, {@link KeyRing}[]].
  */
 
-Wallet.prototype.deriveInputs = spawn.co(function* deriveInputs(tx) {
+Wallet.prototype.deriveInputs = co(function* deriveInputs(tx) {
   var rings = [];
   var i, paths, path, account, ring;
 
@@ -1062,7 +1063,7 @@ Wallet.prototype.deriveInputs = spawn.co(function* deriveInputs(tx) {
  * @param {Function} callback
  */
 
-Wallet.prototype.getKeyRing = spawn.co(function* getKeyRing(address) {
+Wallet.prototype.getKeyRing = co(function* getKeyRing(address) {
   var hash = bcoin.address.getHash(address, 'hex');
   var path, account;
 
@@ -1088,7 +1089,7 @@ Wallet.prototype.getKeyRing = spawn.co(function* getKeyRing(address) {
  * @param {Function} callback - Returns [Error, {@link Path}[]].
  */
 
-Wallet.prototype.getInputPaths = spawn.co(function* getInputPaths(tx) {
+Wallet.prototype.getInputPaths = co(function* getInputPaths(tx) {
   var paths = [];
   var hashes = [];
   var i, hash, path;
@@ -1126,7 +1127,7 @@ Wallet.prototype.getInputPaths = spawn.co(function* getInputPaths(tx) {
  * @param {Function} callback - Returns [Error, {@link Path}[]].
  */
 
-Wallet.prototype.getOutputPaths = spawn.co(function* getOutputPaths(tx) {
+Wallet.prototype.getOutputPaths = co(function* getOutputPaths(tx) {
   var paths = [];
   var hashes = [];
   var i, hash, path;
@@ -1158,7 +1159,7 @@ Wallet.prototype.getOutputPaths = spawn.co(function* getOutputPaths(tx) {
  * (true if new addresses were allocated).
  */
 
-Wallet.prototype.syncOutputDepth = spawn.co(function* syncOutputDepth(info) {
+Wallet.prototype.syncOutputDepth = co(function* syncOutputDepth(info) {
   var unlock = yield this._lockWrite();
   var receive = [];
   var accounts = {};
@@ -1246,7 +1247,7 @@ Wallet.prototype.syncOutputDepth = spawn.co(function* syncOutputDepth(info) {
  * @param {Function} callback
  */
 
-Wallet.prototype.updateBalances = spawn.co(function* updateBalances() {
+Wallet.prototype.updateBalances = co(function* updateBalances() {
   var balance;
 
   if (this.db.listeners('balance').length === 0
@@ -1268,7 +1269,7 @@ Wallet.prototype.updateBalances = spawn.co(function* updateBalances() {
  * @param {Function} callback
  */
 
-Wallet.prototype.handleTX = spawn.co(function* handleTX(info) {
+Wallet.prototype.handleTX = co(function* handleTX(info) {
   yield this.syncOutputDepth(info);
   yield this.updateBalances();
 });
@@ -1279,7 +1280,7 @@ Wallet.prototype.handleTX = spawn.co(function* handleTX(info) {
  * @returns {Script}
  */
 
-Wallet.prototype.getRedeem = spawn.co(function* getRedeem(hash) {
+Wallet.prototype.getRedeem = co(function* getRedeem(hash) {
   var ring;
 
   if (typeof hash === 'string')
@@ -1302,7 +1303,7 @@ Wallet.prototype.getRedeem = spawn.co(function* getRedeem(hash) {
  * (total number of scripts built).
  */
 
-Wallet.prototype.template = spawn.co(function* template(tx) {
+Wallet.prototype.template = co(function* template(tx) {
   var total = 0;
   var i, rings, ring;
 
@@ -1325,7 +1326,7 @@ Wallet.prototype.template = spawn.co(function* template(tx) {
  * of inputs scripts built and signed).
  */
 
-Wallet.prototype.sign = spawn.co(function* sign(tx, options) {
+Wallet.prototype.sign = co(function* sign(tx, options) {
   var passphrase, timeout, master, rings;
 
   if (!options)
@@ -1443,7 +1444,7 @@ Wallet.prototype.addTX = function addTX(tx) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-Wallet.prototype.getHistory = spawn.co(function* getHistory(account) {
+Wallet.prototype.getHistory = co(function* getHistory(account) {
   account = yield this._getIndex(account);
   return this.tx.getHistory(account);
 });
@@ -1454,7 +1455,7 @@ Wallet.prototype.getHistory = spawn.co(function* getHistory(account) {
  * @param {Function} callback - Returns [Error, {@link Coin}[]].
  */
 
-Wallet.prototype.getCoins = spawn.co(function* getCoins(account) {
+Wallet.prototype.getCoins = co(function* getCoins(account) {
   account = yield this._getIndex(account);
   return yield this.tx.getCoins(account);
 });
@@ -1465,7 +1466,7 @@ Wallet.prototype.getCoins = spawn.co(function* getCoins(account) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-Wallet.prototype.getUnconfirmed = spawn.co(function* getUnconfirmed(account) {
+Wallet.prototype.getUnconfirmed = co(function* getUnconfirmed(account) {
   account = yield this._getIndex(account);
   return yield this.tx.getUnconfirmed(account);
 });
@@ -1476,7 +1477,7 @@ Wallet.prototype.getUnconfirmed = spawn.co(function* getUnconfirmed(account) {
  * @param {Function} callback - Returns [Error, {@link Balance}].
  */
 
-Wallet.prototype.getBalance = spawn.co(function* getBalance(account) {
+Wallet.prototype.getBalance = co(function* getBalance(account) {
   account = yield this._getIndex(account);
   return yield this.tx.getBalance(account);
 });
@@ -1490,7 +1491,7 @@ Wallet.prototype.getBalance = spawn.co(function* getBalance(account) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-Wallet.prototype.getRange = spawn.co(function* getRange(account, options) {
+Wallet.prototype.getRange = co(function* getRange(account, options) {
   if (account && typeof account === 'object') {
     options = account;
     account = null;
@@ -1506,7 +1507,7 @@ Wallet.prototype.getRange = spawn.co(function* getRange(account, options) {
  * @param {Function} callback - Returns [Error, {@link TX}[]].
  */
 
-Wallet.prototype.getLast = spawn.co(function* getLast(account, limit) {
+Wallet.prototype.getLast = co(function* getLast(account, limit) {
   account = yield this._getIndex(account);
   return yield this.tx.getLast(account, limit);
 });
@@ -1518,7 +1519,7 @@ Wallet.prototype.getLast = spawn.co(function* getLast(account, limit) {
  * @param {Function} callback - Returns [Error].
  */
 
-Wallet.prototype.zap = spawn.co(function* zap(account, age) {
+Wallet.prototype.zap = co(function* zap(account, age) {
   account = yield this._getIndex(account);
   return yield this.tx.zap(account, age);
 });
@@ -1541,7 +1542,7 @@ Wallet.prototype.abandon = function abandon(hash) {
  * @param {Function} callback
  */
 
-Wallet.prototype._getIndex = spawn.co(function* _getIndex(account) {
+Wallet.prototype._getIndex = co(function* _getIndex(account) {
   var index;
 
   if (account == null)
@@ -2017,7 +2018,7 @@ MasterKey.prototype._lock = function _lock(force) {
  * @param {Function} callback - Returns [Error, {@link HDPrivateKey}].
  */
 
-MasterKey.prototype.unlock = spawn.co(function* _unlock(passphrase, timeout) {
+MasterKey.prototype.unlock = co(function* _unlock(passphrase, timeout) {
   var unlock = yield this._lock();
   var data, key;
 
@@ -2135,7 +2136,7 @@ MasterKey.prototype.destroy = function destroy() {
  * @param {Function} callback
  */
 
-MasterKey.prototype.decrypt = spawn.co(function* decrypt(passphrase) {
+MasterKey.prototype.decrypt = co(function* decrypt(passphrase) {
   var unlock = yield this._lock();
   var data;
 
@@ -2176,7 +2177,7 @@ MasterKey.prototype.decrypt = spawn.co(function* decrypt(passphrase) {
  * @param {Function} callback
  */
 
-MasterKey.prototype.encrypt = spawn.co(function* encrypt(passphrase) {
+MasterKey.prototype.encrypt = co(function* encrypt(passphrase) {
   var unlock = yield this._lock();
   var data, iv;
 
diff --git a/lib/wallet/walletdb.js b/lib/wallet/walletdb.js
index c716f7dc..5e2feba7 100644
--- a/lib/wallet/walletdb.js
+++ b/lib/wallet/walletdb.js
@@ -11,6 +11,7 @@ var bcoin = require('../env');
 var AsyncObject = require('../utils/async');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var crypto = require('../crypto/crypto');
 var assert = utils.assert;
 var constants = bcoin.constants;
@@ -225,7 +226,7 @@ WalletDB.prototype._lockTX = function _lockTX(force) {
  * @param {Function} callback
  */
 
-WalletDB.prototype._open = spawn.co(function* open() {
+WalletDB.prototype._open = co(function* open() {
   yield this.db.open();
   yield this.db.checkVersion('V', 2);
   yield this.writeGenesis();
@@ -245,7 +246,7 @@ WalletDB.prototype._open = spawn.co(function* open() {
  * @param {Function} callback
  */
 
-WalletDB.prototype._close = spawn.co(function* close() {
+WalletDB.prototype._close = co(function* close() {
   var keys = Object.keys(this.wallets);
   var i, key, wallet;
 
@@ -274,7 +275,7 @@ WalletDB.prototype.backup = function backup(path) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.getDepth = spawn.co(function* getDepth() {
+WalletDB.prototype.getDepth = co(function* getDepth() {
   var kv, iter, depth;
 
   // This may seem like a strange way to do
@@ -404,7 +405,7 @@ WalletDB.prototype.testFilter = function testFilter(hashes) {
  * @param {Function} callback - Returns [Error, Object].
  */
 
-WalletDB.prototype.dump = spawn.co(function* dump() {
+WalletDB.prototype.dump = co(function* dump() {
   var records = {};
   yield this.db.iterate({
     gte: ' ',
@@ -472,7 +473,7 @@ WalletDB.prototype.getWalletID = function getWalletID(id) {
  * @param {Function} callback - Returns [Error, {@link Wallet}].
  */
 
-WalletDB.prototype.get = spawn.co(function* get(wid) {
+WalletDB.prototype.get = co(function* get(wid) {
   var self = this;
   var wallet, unlock;
 
@@ -535,7 +536,7 @@ WalletDB.prototype.save = function save(wallet) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.auth = spawn.co(function* auth(wid, token) {
+WalletDB.prototype.auth = co(function* auth(wid, token) {
   var wallet = yield this.get(wid);
   if (!wallet)
     return;
@@ -559,7 +560,7 @@ WalletDB.prototype.auth = spawn.co(function* auth(wid, token) {
  * @param {Function} callback - Returns [Error, {@link Wallet}].
  */
 
-WalletDB.prototype.create = spawn.co(function* create(options) {
+WalletDB.prototype.create = co(function* create(options) {
   var unlock, wallet, exists;
 
   if (!options)
@@ -596,7 +597,7 @@ WalletDB.prototype.create = spawn.co(function* create(options) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.has = spawn.co(function* has(id) {
+WalletDB.prototype.has = co(function* has(id) {
   var wid = yield this.getWalletID(id);
   return wid != null;
 });
@@ -607,7 +608,7 @@ WalletDB.prototype.has = spawn.co(function* has(id) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.ensure = spawn.co(function* ensure(options) {
+WalletDB.prototype.ensure = co(function* ensure(options) {
   var wallet = yield this.get(options.id);
   if (wallet)
     return wallet;
@@ -621,7 +622,7 @@ WalletDB.prototype.ensure = spawn.co(function* ensure(options) {
  * @param {Function} callback - Returns [Error, {@link Wallet}].
  */
 
-WalletDB.prototype.getAccount = spawn.co(function* getAccount(wid, name) {
+WalletDB.prototype.getAccount = co(function* getAccount(wid, name) {
   var index = yield this.getAccountIndex(wid, name);
   var account;
 
@@ -666,7 +667,7 @@ WalletDB.prototype._getAccount = function getAccount(wid, index) {
  * @param {Function} callback - Returns [Error, Array].
  */
 
-WalletDB.prototype.getAccounts = spawn.co(function* getAccounts(wid) {
+WalletDB.prototype.getAccounts = co(function* getAccounts(wid) {
   var map = [];
   var i, accounts;
 
@@ -699,7 +700,7 @@ WalletDB.prototype.getAccounts = spawn.co(function* getAccounts(wid) {
  * @param {Function} callback - Returns [Error, Number].
  */
 
-WalletDB.prototype.getAccountIndex = spawn.co(function* getAccountIndex(wid, name) {
+WalletDB.prototype.getAccountIndex = co(function* getAccountIndex(wid, name) {
   var index;
 
   if (!wid)
@@ -744,7 +745,7 @@ WalletDB.prototype.saveAccount = function saveAccount(account) {
  * @param {Function} callback - Returns [Error, {@link Account}].
  */
 
-WalletDB.prototype.createAccount = spawn.co(function* createAccount(options) {
+WalletDB.prototype.createAccount = co(function* createAccount(options) {
   var exists = yield this.hasAccount(options.wid, options.name);
   var account;
 
@@ -770,7 +771,7 @@ WalletDB.prototype.createAccount = spawn.co(function* createAccount(options) {
  * @param {Function} callback - Returns [Error, Boolean].
  */
 
-WalletDB.prototype.hasAccount = spawn.co(function* hasAccount(wid, account) {
+WalletDB.prototype.hasAccount = co(function* hasAccount(wid, account) {
   var index, key;
 
   if (!wid)
@@ -798,7 +799,7 @@ WalletDB.prototype.hasAccount = spawn.co(function* hasAccount(wid, account) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.saveAddress = spawn.co(function* saveAddress(wid, rings) {
+WalletDB.prototype.saveAddress = co(function* saveAddress(wid, rings) {
   var i, ring, path;
 
   for (i = 0; i < rings.length; i++) {
@@ -823,7 +824,7 @@ WalletDB.prototype.saveAddress = spawn.co(function* saveAddress(wid, rings) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.writeAddress = spawn.co(function* writeAddress(wid, address, path) {
+WalletDB.prototype.writeAddress = co(function* writeAddress(wid, address, path) {
   var hash = address.getHash('hex');
   var batch = this.batch(wid);
   var paths;
@@ -854,7 +855,7 @@ WalletDB.prototype.writeAddress = spawn.co(function* writeAddress(wid, address,
  * @param {Function} callback
  */
 
-WalletDB.prototype.getAddressPaths = spawn.co(function* getAddressPaths(hash) {
+WalletDB.prototype.getAddressPaths = co(function* getAddressPaths(hash) {
   var paths;
 
   if (!hash)
@@ -885,7 +886,7 @@ WalletDB.prototype.getAddressPaths = spawn.co(function* getAddressPaths(hash) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.hasAddress = spawn.co(function* hasAddress(wid, hash) {
+WalletDB.prototype.hasAddress = co(function* hasAddress(wid, hash) {
   var paths = yield this.getAddressPaths(hash);
 
   if (!paths || !paths[wid])
@@ -961,7 +962,7 @@ WalletDB.prototype.getWallets = function getWallets() {
  * @param {Function} callback
  */
 
-WalletDB.prototype.rescan = spawn.co(function* rescan(chaindb, height) {
+WalletDB.prototype.rescan = co(function* rescan(chaindb, height) {
   var self = this;
   var unlock = yield this._lockTX();
   var hashes;
@@ -1024,7 +1025,7 @@ WalletDB.prototype.getPendingKeys = function getPendingKeys() {
  * @param {Function} callback
  */
 
-WalletDB.prototype.resend = spawn.co(function* resend() {
+WalletDB.prototype.resend = co(function* resend() {
   var self = this;
   var i, keys, key, tx;
 
@@ -1050,7 +1051,7 @@ WalletDB.prototype.resend = spawn.co(function* resend() {
  * @param {Function} callback - Returns [Error, {@link PathInfo[]}].
  */
 
-WalletDB.prototype.mapWallets = spawn.co(function* mapWallets(tx) {
+WalletDB.prototype.mapWallets = co(function* mapWallets(tx) {
   var hashes = tx.getHashes('hex');
   var table;
 
@@ -1071,7 +1072,7 @@ WalletDB.prototype.mapWallets = spawn.co(function* mapWallets(tx) {
  * @param {Function} callback - Returns [Error, {@link PathInfo}].
  */
 
-WalletDB.prototype.getPathInfo = spawn.co(function* getPathInfo(wallet, tx) {
+WalletDB.prototype.getPathInfo = co(function* getPathInfo(wallet, tx) {
   var hashes = tx.getHashes('hex');
   var table = yield this.getTable(hashes);
   var info;
@@ -1091,7 +1092,7 @@ WalletDB.prototype.getPathInfo = spawn.co(function* getPathInfo(wallet, tx) {
  * @param {Function} callback - Returns [Error, {@link AddressTable}].
  */
 
-WalletDB.prototype.getTable = spawn.co(function* getTable(hashes) {
+WalletDB.prototype.getTable = co(function* getTable(hashes) {
   var table = {};
   var count = 0;
   var i, j, keys, values, hash, paths;
@@ -1128,7 +1129,7 @@ WalletDB.prototype.getTable = spawn.co(function* getTable(hashes) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.writeGenesis = spawn.co(function* writeGenesis() {
+WalletDB.prototype.writeGenesis = co(function* writeGenesis() {
   var block = yield this.getTip();
   if (block) {
     this.tip = block.hash;
@@ -1156,7 +1157,7 @@ WalletDB.prototype.getTip = function getTip() {
  * @param {Function} callback
  */
 
-WalletDB.prototype.setTip = spawn.co(function* setTip(hash, height) {
+WalletDB.prototype.setTip = co(function* setTip(hash, height) {
   var block = new WalletBlock(hash, height);
 
   yield this.db.put(layout.R, block.toTip());
@@ -1234,7 +1235,7 @@ WalletDB.prototype.getWalletsByTX = function getWalletsByTX(hash) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.addBlock = spawn.co(function* addBlock(entry, txs, force) {
+WalletDB.prototype.addBlock = co(function* addBlock(entry, txs, force) {
   var unlock = yield this._lockTX(force);
   var i, block, matches, hash, tx, wallets;
 
@@ -1302,7 +1303,7 @@ WalletDB.prototype.addBlock = spawn.co(function* addBlock(entry, txs, force) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.removeBlock = spawn.co(function* removeBlock(entry) {
+WalletDB.prototype.removeBlock = co(function* removeBlock(entry) {
   var unlock = yield this._lockTX();
   var i, j, block, data, hash, wallets, wid, wallet;
 
@@ -1360,7 +1361,7 @@ WalletDB.prototype.removeBlock = spawn.co(function* removeBlock(entry) {
  * @param {Function} callback - Returns [Error].
  */
 
-WalletDB.prototype.addTX = spawn.co(function* addTX(tx, force) {
+WalletDB.prototype.addTX = co(function* addTX(tx, force) {
   var unlock = yield this._lockTX(force);
   var i, wallets, info, wallet;
 
@@ -1417,7 +1418,7 @@ WalletDB.prototype.addTX = spawn.co(function* addTX(tx, force) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.getAddressPath = spawn.co(function* getAddressPath(wid, hash) {
+WalletDB.prototype.getAddressPath = co(function* getAddressPath(wid, hash) {
   var paths = yield this.getAddressPaths(hash);
   var path;
 
diff --git a/lib/workers/workers.js b/lib/workers/workers.js
index 8055598f..39873583 100644
--- a/lib/workers/workers.js
+++ b/lib/workers/workers.js
@@ -12,6 +12,7 @@ var EventEmitter = require('events').EventEmitter;
 var bn = require('bn.js');
 var utils = require('../utils/utils');
 var spawn = require('../utils/spawn');
+var co = spawn.co;
 var global = utils.global;
 var assert = utils.assert;
 var BufferWriter = require('../utils/writer');
@@ -247,7 +248,7 @@ Workers.prototype.verify = function verify(tx, flags) {
  * @param {Function} callback
  */
 
-Workers.prototype.sign = spawn.co(function* sign(tx, ring, type) {
+Workers.prototype.sign = co(function* sign(tx, ring, type) {
   var i, result, input, sig, sigs, total;
 
   result = yield this.execute('sign', [tx, ring, type], -1);