diff --git a/lib/bcoin/mtx.js b/lib/bcoin/mtx.js
index a38804fc..c310682a 100644
--- a/lib/bcoin/mtx.js
+++ b/lib/bcoin/mtx.js
@@ -539,8 +539,8 @@ MTX.prototype.signInput = function signInput(index, addr, type) {
   return signatures === m;
 };
 
-MTX.prototype.isSigned = function isSigned(m) {
-  var i, input, prev, vector, len, j;
+MTX.prototype.isSigned = function isSigned() {
+  var i, input, prev, vector, m, len, j;
   var total = 0;
 
   for (i = 0; i < this.inputs.length; i++) {
@@ -567,10 +567,7 @@ MTX.prototype.isSigned = function isSigned(m) {
 
     // If the output script is a witness program,
     // we have to switch the vector to the witness
-    // and potentially alter the length. Note that
-    // witnesses are stack items, so the `dummy`
-    // _has_ to be an empty buffer (what OP_0
-    // pushes onto the stack).
+    // and potentially alter the length.
     if (prev.isWitnessScripthash()) {
       prev = input.witness.getRedeem();
       vector = input.witness.items;
@@ -602,13 +599,7 @@ MTX.prototype.isSigned = function isSigned(m) {
       if (len - 1 !== m)
         return false;
     } else {
-      for (j = 0; j < vector.length; j++) {
-        if (Script.isSignatureEncoding(vector[j]))
-          total++;
-      }
-
-      if (total !== m)
-        return false;
+      return false;
     }
   }
 
@@ -684,15 +675,25 @@ MTX.prototype.scriptOutput = function scriptOutput(index, options) {
 };
 
 MTX.prototype.isScripted = function isScripted() {
-  if (this.inputs.length === 0)
-    return false;
+  var i, input;
 
   if (this.outputs.length === 0)
     return false;
 
-  return this.inputs.every(function(input) {
-    return input.script.code.length > 0 || input.witness.items.length > 0;
-  });
+  if (this.inputs.length === 0)
+    return false;
+
+  for (i = 0; i < this.inputs.length; i++) {
+    input = this.inputs[i];
+
+    if (input.script.code.length === 0)
+      return false;
+
+    if (input.witness.items.length === 0)
+      return false;
+  }
+
+  return true;
 };
 
 MTX.prototype.maxSize = function maxSize(options, force) {
@@ -855,25 +856,20 @@ MTX.prototype.maxSize = function maxSize(options, force) {
 };
 
 MTX.prototype.selectCoins = function selectCoins(coins, options) {
-  var chosen, lastAdded, tx, outputValue;
-  var i, size, change, fee, tryFree, minValue;
+  var chosen = [];
+  var index = 0;
+  var tx = this.clone();
+  var outputValue = tx.getOutputValue();
+  var tryFree, i, size, change, fee, minValue;
 
-  if (!options || typeof options !== 'object') {
-    options = {
-      changeAddress: arguments[1],
-      fee: arguments[2]
-    };
-  }
+  if (!options)
+    options = {};
 
-  tx = this.clone();
-  tx.inputs.length = 0;
-
-  chosen = [];
-  lastAdded = 0;
-
-  outputValue = tx.getOutputValue();
   tryFree = options.free;
 
+  // Null the inputs if there are any.
+  tx.inputs.length = 0;
+
   if (options.confirmed) {
     coins = coins.filter(function(coin) {
       return coin.height !== -1;
@@ -895,7 +891,7 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
   }
 
   function total() {
-    if (options.subtractFee)
+    if (options.subtractFee != null)
       return outputValue;
     return outputValue.add(fee);
   }
@@ -905,15 +901,13 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
   }
 
   function addCoins() {
-    var i, index;
-
-    for (i = lastAdded; i < coins.length; i++) {
+    while (index < coins.length) {
       // Add new inputs until TX will have enough
       // funds to cover both minimum post cost
       // and fee.
-      tx.addInput(coins[i]);
-      chosen.push(coins[i]);
-      lastAdded++;
+      tx.addInput(coins[index]);
+      chosen.push(coins[index]);
+      index++;
 
       if (options.selection === 'all')
         continue;
@@ -939,6 +933,9 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
     // calculate maximum TX size.
     tx.addOutput({
       address: options.changeAddress,
+      // In case we don't have a change address,
+      // use a fake p2pkh output to gauge size.
+      keyHash: constants.zeroHash.slice(0, 20),
       value: new bn(0)
     });
 
@@ -961,10 +958,10 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
       else
         fee = tx.getMaxFee(size);
 
-      // Failed to get enough funds, add more inputs.
+      // Failed to get enough funds, add more coins.
       if (!isFull())
         addCoins();
-    } while (!isFull() && lastAdded < coins.length);
+    } while (!isFull() && index < coins.length);
   }
 
   if (!isFull()) {
@@ -1012,50 +1009,37 @@ MTX.prototype.selectCoins = function selectCoins(coins, options) {
 };
 
 MTX.prototype.fill = function fill(coins, options) {
-  var self = this;
-  var result, err;
+  var result, i;
 
   assert(this.ts === 0, 'Cannot modify a confirmed tx.');
   assert(this.inputs.length === 0, 'TX is already filled.');
-
-  if (!options || typeof options !== 'object') {
-    options = {
-      changeAddress: arguments[1],
-      fee: arguments[2]
-    };
-  }
-
-  assert(coins);
+  assert(options, '`options` are required.');
   assert(options.changeAddress, '`changeAddress` is required.');
 
+  // Select necessary coins.
   result = this.selectCoins(coins, options);
 
-  result.coins.forEach(function(coin) {
-    self.addInput(coin);
-  });
+  // Add coins to transaction.
+  for (i = 0; i < result.coins.length; i++)
+    this.addInput(result.coins[i]);
 
   if (result.change.cmpn(constants.tx.dustThreshold) < 0) {
     // Do nothing. Change is added to fee.
-    assert.equal(
-      this.getFee().toNumber(),
-      result.fee.add(result.change).toNumber()
-    );
+    assert(this.getFee().cmp(result.fee.add(result.change)) === 0);
     this.changeIndex = -1;
   } else {
+    // Add a change output.
     this.addOutput({
       address: options.changeAddress,
       value: result.change
     });
-
     this.changeIndex = this.outputs.length - 1;
-
-    assert.equal(this.getFee().toNumber(), result.fee.toNumber());
+    assert(this.getFee().cmp(result.fee) === 0);
   }
 
   return result;
 };
 
-// https://github.com/bitcoin/bips/blob/master/bip-0069.mediawiki
 MTX.prototype.sortMembers = function sortMembers() {
   var changeOutput;
 
diff --git a/lib/bcoin/wallet.js b/lib/bcoin/wallet.js
index 7a1b1f08..59b9fe2c 100644
--- a/lib/bcoin/wallet.js
+++ b/lib/bcoin/wallet.js
@@ -202,6 +202,8 @@ Wallet.prototype.addKey = function addKey(key) {
   if (key instanceof bcoin.hd.privateKey)
     key = key.hdPublicKey;
 
+  assert(key instanceof bcoin.hd, 'Must add HD keys to wallet.');
+
   if (this.derivation === 'bip44') {
     if (!key || !key.isAccount44())
       throw new Error('Must add HD account keys to BIP44 wallet.');
@@ -246,6 +248,8 @@ Wallet.prototype.removeKey = function removeKey(key) {
   if (key instanceof bcoin.hd.privateKey)
     key = key.hdPublicKey;
 
+  assert(key instanceof bcoin.hd, 'Must add HD keys to wallet.');
+
   if (this.derivation === 'bip44') {
     if (!key || !key.isAccount44())
       throw new Error('Must add HD account keys to BIP44 wallet.');
@@ -616,6 +620,10 @@ Wallet.prototype.createTX = function createTX(options, outputs, callback) {
   });
 };
 
+Wallet.prototype.deriveInput = function deriveInput(tx, i) {
+  return this.deriveInputs(tx.inputs[i])[0];
+};
+
 Wallet.prototype.deriveInputs = function deriveInputs(tx) {
   var paths = this.getInputPaths(tx);
   var addresses = [];
@@ -731,7 +739,7 @@ Wallet.prototype.getRedeem = function getRedeem(hash, prefix) {
     else if (hash.length === 32)
       prefix = 'witnessscripthash';
     else
-      assert(false, 'Unknown hash length.');
+      return;
   }
 
   addr = bcoin.address.compileHash(hash, prefix);
@@ -759,8 +767,9 @@ Wallet.prototype.zap = function zap(now, age, callback) {
 Wallet.prototype.scan = function scan(txByAddress, callback) {
   var self = this;
   var res = false;
+  var i;
 
-  return this._scan({}, txByAddress, function(err, depth) {
+  return this._scan({}, txByAddress, function(err, depth, txs) {
     if (err)
       return callback(err);
 
@@ -770,25 +779,50 @@ Wallet.prototype.scan = function scan(txByAddress, callback) {
     if (self.setReceiveDepth(depth.receiveDepth + 1))
       res = true;
 
-    return callback(null, res);
+    if (self.provider && self.provider.addTX) {
+      utils.forEachSerial(txs, function(tx, next) {
+        self.addTX(tx, next);
+      }, function(err) {
+        if (err)
+          return callback(err);
+        return callback(null, res, txs);
+      });
+      return;
+    }
+
+    return callback(null, res, txs);
   });
 };
 
+Wallet.prototype.clone = function clone() {
+  var passphrase = this.options.passphrase;
+  var wallet;
+
+  delete this.options.passphrase;
+
+  wallet = Wallet.fromJSON(this.toJSON());
+
+  this.options.passphrase = passphrase;
+
+  return wallet;
+};
+
 Wallet.prototype._scan = function _scan(options, txByAddress, callback) {
-  var self = this;
   var depth = { changeDepth: 0, receiveDepth: 0 };
+  var wallet = this.clone();
+  var all = [];
 
   assert(this._initialized);
 
-  return (function chainCheck(change) {
+  (function chainCheck(change) {
     var addressIndex = 0;
     var total = 0;
     var gap = 0;
 
-    return (function next() {
-      var address = self.deriveAddress(change, addressIndex++);
+    (function next() {
+      var address = wallet.deriveAddress(change, addressIndex++);
 
-      return txByAddress(address.getAddress(), function(err, txs) {
+      txByAddress(address.getAddress(), function(err, txs) {
         var result;
 
         if (err)
@@ -805,7 +839,7 @@ Wallet.prototype._scan = function _scan(options, txByAddress, callback) {
             result = false;
 
           if (Array.isArray(txs) && (txs[0] instanceof bcoin.tx))
-            txs.forEach(function(tx) { self.addTX(tx); });
+            all = all.concat(txs);
         }
 
         if (result) {
@@ -827,7 +861,7 @@ Wallet.prototype._scan = function _scan(options, txByAddress, callback) {
         if (change === false)
           return chainCheck(true);
 
-        return callback(null, depth);
+        return callback(null, depth, all);
       });
     })();
   })(false);
@@ -835,26 +869,35 @@ Wallet.prototype._scan = function _scan(options, txByAddress, callback) {
 
 Wallet.prototype.scriptInputs = function scriptInputs(tx, index) {
   var addresses = this.deriveInputs(tx);
+  var total = 0;
+  var i;
 
-  return addresses.reduce(function(total, address) {
-    return total + address.scriptInputs(tx, index);
-  }, 0);
+  for (i = 0; i < addresses.length; i++)
+    total += addresses[i].scriptInputs(tx, index);
+
+  return total;
 };
 
 Wallet.prototype.signInputs = function signInputs(tx, type, index) {
   var addresses = this.deriveInputs(tx);
+  var total = 0;
+  var i;
 
-  return addresses.reduce(function(total, address) {
-    return total + address.signInputs(tx, type, index);
-  }, 0);
+  for (i = 0; i < addresses.length; i++)
+    total += addresses[i].signInputs(tx, type, index);
+
+  return total;
 };
 
 Wallet.prototype.sign = function sign(tx, type, index) {
   var addresses = this.deriveInputs(tx);
+  var total = 0;
+  var i;
 
-  return addresses.reduce(function(total, address) {
-    return total + address.sign(tx, type, index);
-  }, 0);
+  for (i = 0; i < addresses.length; i++)
+    total += addresses[i].sign(tx, type, index);
+
+  return total;
 };
 
 Wallet.prototype.addTX = function addTX(tx, callback) {