diff --git a/lib/chain/chaindb.js b/lib/chain/chaindb.js
index 01c9b191..3cafbcf2 100644
--- a/lib/chain/chaindb.js
+++ b/lib/chain/chaindb.js
@@ -1231,7 +1231,7 @@ ChainDB.prototype.scan = function scan(start, filter, iter) {
         }
       }
 
-      yield iter(entry, txs);
+      yield* iter(entry, txs);
       entry = yield entry.getNext();
     }
 
diff --git a/lib/http/rpc.js b/lib/http/rpc.js
index 663b78a8..787bc21b 100644
--- a/lib/http/rpc.js
+++ b/lib/http/rpc.js
@@ -285,7 +285,7 @@ RPC.prototype.execute = function execute(json) {
       return this.getmemory(json.params);
 
     default:
-      return callback(new Error('Method not found: ' + json.method + '.'));
+      throw new Error('Method not found: ' + json.method + '.');
   }
 };
 
@@ -432,7 +432,7 @@ RPC.prototype.getaddednodeinfo = function getaddednodeinfo(args) {
     addr = NetworkAddress.fromHostname(host, this.network);
     peer = this.pool.peers.get(addr);
     if (!peer)
-      return callback(new RPCError('Node has not been added.'));
+      return Promise.reject(new RPCError('Node has not been added.'));
     peers = [peer];
   } else {
     peers = this.pool.peers.all;
@@ -842,7 +842,7 @@ RPC.prototype.getblockhash = function getblockhash(args) {
     entry = yield this.chain.db.get(height);
 
     if (!entry)
-      return callback(new RPCError('Not found.'));
+      throw new RPCError('Not found.');
 
     return entry.rhash;
   }, this);
@@ -934,10 +934,10 @@ RPC.prototype._blockToJSON = function _blockToJSON(entry, block, txDetails) {
   }, this);
 };
 
-RPC.prototype.getchaintips = function getchaintips(args, callback) {
+RPC.prototype.getchaintips = function getchaintips(args) {
   return spawn(function *() {
     var i, tips, orphans, prevs, result;
-    var orphan, entires, entry, main, fork;
+    var orphan, entries, entry, main, fork;
 
     if (args.help || args.length !== 0)
       throw new RPCError('getchaintips');
@@ -1211,7 +1211,6 @@ RPC.prototype.gettxout = function gettxout(args) {
 
 RPC.prototype.gettxoutproof = function gettxoutproof(args) {
   return spawn(function *() {
-    var self = this;
     var uniq = {};
     var i, txids, block, hash, last, tx, coins;
 
@@ -1281,7 +1280,7 @@ RPC.prototype.gettxoutproof = function gettxoutproof(args) {
 RPC.prototype.verifytxoutproof = function verifytxoutproof(args) {
   return spawn(function *() {
     var res = [];
-    var i, block, hash;
+    var i, block, hash, entry;
 
     if (args.help || args.length !== 1)
       throw new RPCError('verifytxoutproof "proof"');
@@ -1323,7 +1322,7 @@ RPC.prototype.gettxoutsetinfo = function gettxoutsetinfo(args) {
   });
 };
 
-RPC.prototype.verifychain = function verifychain(args, callback) {
+RPC.prototype.verifychain = function verifychain(args) {
   if (args.help || args.length > 2)
     return Promise.reject(new RPCError('verifychain ( checklevel numblocks )'));
 
@@ -1522,7 +1521,7 @@ RPC.prototype.getblocktemplate = function getblocktemplate(args) {
       if (opt.mode != null) {
         mode = opt.mode;
         if (mode !== 'template' && mode !== 'proposal')
-          return callback(new RPCError('Invalid mode.'));
+          throw new RPCError('Invalid mode.');
       }
 
       lpid = opt.longpollid;
@@ -1905,13 +1904,13 @@ RPC.prototype._hashps = function _hashps(lookup, height) {
 
     pb = this.chain.tip;
     if (height >= 0 && height < this.chain.tip.height)
-      pb = yield this.chain.db.get(height, callback);
+      pb = yield this.chain.db.get(height);
 
     if (!pb)
       return 0;
 
     if (lookup <= 0)
-      lookup = pb.height % self.network.pow.retargetInterval + 1;
+      lookup = pb.height % this.network.pow.retargetInterval + 1;
 
     if (lookup > pb.height)
       lookup = pb.height;
@@ -1987,6 +1986,7 @@ RPC.prototype.generate = function generate(args) {
 RPC.prototype._generate = function _generate(numblocks) {
   return spawn(function *() {
     var hashes = [];
+    var i, block;
 
     for (i = 0; i < numblocks; i++) {
       block = yield this.miner.mineBlock();
@@ -2261,7 +2261,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
         secret = k[i];
 
         if (!utils.isBase58(secret))
-          return callback(new RPCError('Invalid parameter'));
+          throw new RPCError('Invalid parameter');
 
         key = bcoin.keyring.fromSecret(secret);
         keyMap[key.getPublicKey('hex')] = key;
@@ -2277,7 +2277,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
         prev = prevout[i];
 
         if (!prev)
-          return callback(new RPCError('Invalid parameter'));
+          throw new RPCError('Invalid parameter');
 
         hash = toHash(prev.txid);
         index = prev.vout;
@@ -2288,7 +2288,7 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
             || !utils.isNumber(index)
             || index < 0
             || !utils.isHex(script)) {
-          return callback(new RPCError('Invalid parameter'));
+          throw new RPCError('Invalid parameter');
         }
 
         script = bcoin.script.fromRaw(script, 'hex');
@@ -2330,12 +2330,12 @@ RPC.prototype._signrawtransaction = function signrawtransaction(merged, txs, arg
       parts = args[3].split('|');
       type = constants.hashType[parts[0]];
       if (type == null)
-        return callback(new RPCError('Invalid parameter'));
+        throw new RPCError('Invalid parameter');
       if (parts.length > 2)
-        return callback(new RPCError('Invalid parameter'));
+        throw new RPCError('Invalid parameter');
       if (parts.length === 2) {
         if (parts[1] !== 'ANYONECANPAY')
-          return callback(new RPCError('Invalid parameter'));
+          throw new RPCError('Invalid parameter');
         type |= constants.hashType.ANYONECANPAY;
       }
     }
@@ -2522,7 +2522,7 @@ RPC.prototype.validateaddress = function validateaddress(args) {
 
     json = {
       isvalid: true,
-      address: address.toBase58(self.network),
+      address: address.toBase58(this.network),
       scriptPubKey: address.toScript().toJSON(),
       ismine: path ? true : false,
       iswatchonly: false
@@ -2764,7 +2764,7 @@ RPC.prototype.addmultisigaddress = function addmultisigaddress(args) {
   Promise.reject(new Error('Not implemented.'));
 };
 
-RPC.prototype.addwitnessaddress = function addwitnessaddress(args, callback) {
+RPC.prototype.addwitnessaddress = function addwitnessaddress(args) {
   if (args.help || args.length < 1 || args.length > 1)
     return Promise.reject(new RPCError('addwitnessaddress "address"'));
   // Unlikely to be implemented.
@@ -2950,7 +2950,7 @@ RPC.prototype.getaddressesbyaccount = function getaddressesbyaccount(args) {
 
     for (i = 0; i < paths.length; i++) {
       path = paths[i];
-      addrs.push(path.toAddress().toBase58(self.network));
+      addrs.push(path.toAddress().toBase58(this.network));
     }
 
     return addrs;
@@ -3113,7 +3113,7 @@ RPC.prototype.getreceivedbyaddress = function getreceivedbyaddress(args) {
   }, this);
 };
 
-RPC.prototype._toWalletTX = function _toWalletTX(tx, callback) {
+RPC.prototype._toWalletTX = function _toWalletTX(tx) {
   return spawn(function *() {
     var i, det, receive, member, sent, received, json, details;
 
@@ -3192,7 +3192,7 @@ RPC.prototype._toWalletTX = function _toWalletTX(tx, callback) {
   }, this);
 };
 
-RPC.prototype.gettransaction = function gettransaction(args, callback) {
+RPC.prototype.gettransaction = function gettransaction(args) {
   return spawn(function *() {
     var hash, tx;
 
@@ -3337,11 +3337,7 @@ RPC.prototype.importwallet = function importwallet(args) {
       if (parts.length < 4)
         throw new RPCError('Malformed wallet.');
 
-      try {
-        secret = bcoin.keyring.fromSecret(parts[0]);
-      } catch (e) {
-        return callback(e);
-      }
+      secret = bcoin.keyring.fromSecret(parts[0]);
 
       time = +parts[1];
       label = parts[2];
@@ -3591,7 +3587,7 @@ RPC.prototype._listReceived = function _listReceived(minconf, empty, account) {
 RPC.prototype.listsinceblock = function listsinceblock(args) {
   return spawn(function *() {
     var block, conf, out, highest;
-    var i, height, txs, tx;
+    var i, height, txs, tx, json;
 
     if (args.help) {
       throw new RPCError('listsinceblock'
@@ -3789,10 +3785,10 @@ RPC.prototype.listunspent = function listunspent(args) {
         hash = bcoin.address.getHash(address, 'hex');
 
         if (!hash)
-          return callback(new RPCError('Invalid address.'));
+          throw new RPCError('Invalid address.');
 
         if (addresses[hash])
-          return callback(new RPCError('Duplicate address.'));
+          throw new RPCError('Duplicate address.');
 
         addresses[hash] = true;
       }
@@ -3857,7 +3853,7 @@ RPC.prototype.lockunspent = function lockunspent(args) {
   if (args.length === 1) {
     if (unlock)
       this.wallet.tx.unlockCoins();
-    return callback(null, true);
+    return Promise.resolve(true);
   }
 
   outputs = toArray(args[1]);
@@ -4036,7 +4032,7 @@ RPC.prototype.settxfee = function settxfee(args) {
 
 RPC.prototype.signmessage = function signmessage(args) {
   return spawn(function *() {
-    var address, msg, sig;
+    var address, msg, sig, ring;
 
     if (args.help || args.length !== 2)
       throw new RPCError('signmessage "bitcoinaddress" "message"');
@@ -4282,7 +4278,13 @@ function reverseEndian(data) {
 
 function writeFile(file, data) {
   return new Promise(function(resolve, reject) {
-    fs.writeFile(file, out, utils.P(resolve, reject));
+    fs.writeFile(file, data, utils.P(resolve, reject));
+  });
+}
+
+function readFile(file, enc) {
+  return new Promise(function(resolve, reject) {
+    fs.readFile(file, enc, utils.P(resolve, reject));
   });
 }
 
diff --git a/lib/http/server.js b/lib/http/server.js
index 3cddad5a..a62dc1ce 100644
--- a/lib/http/server.js
+++ b/lib/http/server.js
@@ -1338,13 +1338,13 @@ ClientSocket.prototype.scan = function scan(start) {
   if (this.chain.db.options.prune)
     return Promise.reject(new Error('Cannot scan in pruned mode.'));
 
-  return this.chain.db.scan(start, this.filter, function(entry, txs) {
+  return this.chain.db.scan(start, this.filter, function *(entry, txs) {
     for (i = 0; i < txs.length; i++)
       txs[i] = txs[i].toJSON();
 
     self.emit('block tx', entry.toJSON(), txs);
 
-    return Promise.resolve(null);
+    yield utils.wait();
   });
 };
 
diff --git a/lib/net/pool.js b/lib/net/pool.js
index 09ca274d..4303777f 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -1741,7 +1741,6 @@ Pool.prototype.broadcast = function broadcast(msg) {
 
   return new Promise(function(resolve, reject) {
     item.addCallback(utils.P(resolve, reject));
-    return item;
   });
 };
 
@@ -1876,7 +1875,7 @@ Pool.prototype.isIgnored = function isIgnored(addr) {
 
 Pool.prototype.getIP = function getIP() {
   return spawn(function *() {
-    var request, ip, res;
+    var request, res, ip;
 
     if (utils.isBrowser)
       throw new Error('Could not find IP.');
@@ -1910,7 +1909,7 @@ Pool.prototype.getIP = function getIP() {
 
 Pool.prototype.getIP2 = function getIP2() {
   return spawn(function *() {
-    var request, ip;
+    var request, res, ip;
 
     if (utils.isBrowser)
       throw new Error('Could not find IP.');
diff --git a/lib/wallet/walletdb.js b/lib/wallet/walletdb.js
index 85572636..3a84fdff 100644
--- a/lib/wallet/walletdb.js
+++ b/lib/wallet/walletdb.js
@@ -545,7 +545,7 @@ WalletDB.prototype.save = function save(wallet) {
  * @param {Function} callback
  */
 
-WalletDB.prototype.auth = function auth(wid, token, callback) {
+WalletDB.prototype.auth = function auth(wid, token) {
   return spawn(function *() {
     var wallet = yield this.get(wid);
     if (!wallet)
@@ -1011,8 +1011,8 @@ WalletDB.prototype.rescan = function rescan(chaindb, height) {
     this.logger.info('Scanning for %d addresses.', hashes.length);
 
     try {
-      yield chaindb.scan(height, hashes, function(block, txs) {
-        return self.addBlock(block, txs, true);
+      yield chaindb.scan(height, hashes, function *(block, txs) {
+        yield self.addBlock(block, txs, true);
       });
     } catch (e) {
       unlock();
diff --git a/lib/workers/workers.js b/lib/workers/workers.js
index b93defce..2f1f11e1 100644
--- a/lib/workers/workers.js
+++ b/lib/workers/workers.js
@@ -530,7 +530,7 @@ Worker.prototype.destroy = function destroy() {
 Worker.prototype._execute = function _execute(method, args, timeout, callback) {
   var self = this;
   var job = this.uid;
-  var event, timer, callback;
+  var event, timer;
 
   if (++this.uid === 0x100000000)
     this.uid = 0;
diff --git a/test/chain-test.js b/test/chain-test.js
index 1740ccaf..c2b8a0a7 100644
--- a/test/chain-test.js
+++ b/test/chain-test.js
@@ -248,9 +248,9 @@ describe('Chain', function() {
     var total = 0;
     c(walletdb.getAddressHashes(), function(err, hashes) {
       assert.ifError(err);
-      c(chain.db.scan(null, hashes, function(block, txs) {
+      c(chain.db.scan(null, hashes, function *(block, txs) {
         total += txs.length;
-        return Promise.resolve(null);
+        yield utils.wait();
       }), function(err) {
         assert.ifError(err);
         assert.equal(total, 25);