diff --git a/lib/http/server.js b/lib/http/server.js
index 4da98233..b0c9fd88 100644
--- a/lib/http/server.js
+++ b/lib/http/server.js
@@ -231,6 +231,12 @@ HTTPServer.prototype._init = function _init() {
       assert(utils.isUInt32(options.age), 'Age must be a number.');
     }
 
+    if (params.confirmations != null) {
+      options.confirmations = Number(params.confirmations);
+      assert(utils.isNumber(options.confirmations),
+        'Confirmations must be a number.');
+    }
+
     if (params.fee)
       options.fee = utils.satoshi(params.fee);
 
diff --git a/lib/primitives/mtx.js b/lib/primitives/mtx.js
index 7ac33f9b..5ac2d31e 100644
--- a/lib/primitives/mtx.js
+++ b/lib/primitives/mtx.js
@@ -1228,20 +1228,20 @@ MTX.prototype.subtractFee = function subtractFee(fee, index) {
  */
 
 MTX.prototype.fund = function fund(coins, options) {
-  var i, result, change, changeAddress;
+  var i, select, change, changeAddress;
 
   assert(this.inputs.length === 0, 'TX is already filled.');
 
   // Select necessary coins.
-  result = this.selectCoins(coins, options);
+  select = this.selectCoins(coins, options);
 
   // We need a change address.
-  changeAddress = result.changeAddress;
+  changeAddress = select.changeAddress;
 
   // If change address is not available,
   // send back to one of the coins' addresses.
-  for (i = 0; i < result.chosen.length && !changeAddress; i++)
-    changeAddress = result.chosen[i].getAddress();
+  for (i = 0; i < select.chosen.length && !changeAddress; i++)
+    changeAddress = select.chosen[i].getAddress();
 
   // Will only happen in rare cases where
   // we're redeeming all non-standard coins.
@@ -1249,17 +1249,17 @@ MTX.prototype.fund = function fund(coins, options) {
     throw new Error('No change address available.');
 
   // Add coins to transaction.
-  for (i = 0; i < result.chosen.length; i++)
-    this.addInput(result.chosen[i]);
+  for (i = 0; i < select.chosen.length; i++)
+    this.addInput(select.chosen[i]);
 
   // Attempt to subtract fee.
-  if (result.shouldSubtract)
-    this.subtractFee(result.fee, result.subtractFee);
+  if (select.shouldSubtract)
+    this.subtractFee(select.fee, select.subtractFee);
 
   // Add a change output.
   this.addOutput({
     address: changeAddress,
-    value: result.change
+    value: select.change
   });
 
   change = this.outputs[this.outputs.length - 1];
@@ -1268,13 +1268,13 @@ MTX.prototype.fund = function fund(coins, options) {
     // Do nothing. Change is added to fee.
     this.outputs.pop();
     this.changeIndex = -1;
-    assert.equal(this.getFee(), result.fee + result.change);
+    assert.equal(this.getFee(), select.fee + select.change);
   } else {
     this.changeIndex = this.outputs.length - 1;
-    assert.equal(this.getFee(), result.fee);
+    assert.equal(this.getFee(), select.fee);
   }
 
-  return result;
+  return select;
 };
 
 /**
@@ -1440,36 +1440,130 @@ function CoinSelector(tx, options) {
   if (!(this instanceof CoinSelector))
     return new CoinSelector(tx, options);
 
-  if (!options)
-    options = {};
-
   this.tx = tx.clone();
   this.coins = [];
-  this.outputValue = -1;
-  this.index = -1;
+  this.outputValue = 0;
+  this.index = 0;
   this.chosen = [];
-  this.change = -1;
-  this.fee = -1;
+  this.change = 0;
+  this.fee = 0;
 
-  this.type = options.selection || 'age';
-  this.shouldSubtract = !!options.subtractFee || options.subtractFee === 0;
-  this.free = options.free || false;
-  this.subtractFee = options.subtractFee || null;
-  this.height = options.height || -1;
-  this.confirmations = options.confirmations || -1;
-  this.hardFee = options.hardFee || null;
-  this.changeAddress = options.changeAddress || null;
-  this.round = options.round || false;
-  this.rate = options.rate || null;
-  this.maxFee = options.maxFee || null;
+  this.selection = 'age';
+  this.shouldSubtract = false;
+  this.subtractFee = null;
+  this.free = false;
+  this.height = -1;
+  this.confirmations = -1;
+  this.hardFee = -1;
+  this.rate = constants.tx.MIN_RELAY;
+  this.maxFee = -1;
+  this.round = false;
+  this.changeAddress = null;
 
   // Needed for size estimation.
-  this.m = options.m || null;
-  this.n = options.n || null;
-  this.witness = options.witness || false;
-  this.script = options.script || null;
+  this.m = null;
+  this.n = null;
+  this.witness = false;
+  this.script = null;
+
+  if (options)
+    this.fromOptions(options);
 }
 
+/**
+ * Initialize selector options.
+ * @param {Object} options
+ * @private
+ */
+
+CoinSelector.prototype.fromOptions = function fromOptions(options) {
+  var addr;
+
+  if (options.selection) {
+    assert(typeof options.selection === 'string');
+    this.selection = options.selection;
+  }
+
+  if (options.subtractFee != null) {
+    this.subtractFee = options.subtractFee;
+    this.shouldSubtract = options.subtractFee !== false;
+  }
+
+  if (options.free != null) {
+    assert(typeof options.free === 'boolean');
+    this.free = options.free;
+  }
+
+  if (options.height != null) {
+    assert(utils.isNumber(options.height));
+    assert(options.height >= -1);
+    this.height = options.height;
+  }
+
+  if (options.confirmations != null) {
+    assert(utils.isNumber(options.confirmations));
+    assert(options.confirmations >= -1);
+    this.confirmations = options.confirmations;
+  }
+
+  if (options.hardFee != null) {
+    assert(utils.isNumber(options.hardFee));
+    assert(options.hardFee >= -1);
+    this.hardFee = options.hardFee;
+  }
+
+  if (options.rate != null) {
+    assert(utils.isNumber(options.rate));
+    assert(options.rate >= 0);
+    this.rate = options.rate;
+  }
+
+  if (options.maxFee != null) {
+    assert(utils.isNumber(options.maxFee));
+    assert(options.maxFee >= -1);
+    this.maxFee = options.maxFee;
+  }
+
+  if (options.round != null) {
+    assert(typeof options.round === 'boolean');
+    this.round = options.round;
+  }
+
+  if (options.changeAddress) {
+    addr = options.changeAddress;
+    if (typeof addr === 'string') {
+      this.changeAddress = bcoin.address.fromBase58(addr);
+    } else {
+      assert(addr instanceof bcoin.address);
+      this.changeAddress = addr;
+    }
+  }
+
+  if (options.m != null) {
+    assert(utils.isNumber(options.m));
+    assert(options.m >= 1);
+    this.m = options.m;
+  }
+
+  if (options.n != null) {
+    assert(utils.isNumber(options.n));
+    assert(options.n >= 1);
+    this.n = options.n;
+  }
+
+  if (options.witness != null) {
+    assert(typeof options.witness === 'boolean');
+    this.witness = options.witness;
+  }
+
+  if (options.script) {
+    assert(options.script instanceof bcoin.script);
+    this.script = options.script;
+  }
+
+  return this;
+};
+
 /**
  * Initialize the selector with coins to select from.
  * @param {Coin[]} coins
@@ -1484,7 +1578,7 @@ CoinSelector.prototype.init = function init(coins) {
   this.fee = 0;
   this.tx.inputs.length = 0;
 
-  switch (this.type) {
+  switch (this.selection) {
     case 'all':
     case 'random':
       this.coins.sort(sortRandom);
@@ -1493,7 +1587,7 @@ CoinSelector.prototype.init = function init(coins) {
       this.coins.sort(sortAge);
       break;
     default:
-      throw new FundingError('Bad selection type: ' + this.type);
+      throw new FundingError('Bad selection type: ' + this.selection);
   }
 };
 
@@ -1526,18 +1620,17 @@ CoinSelector.prototype.isFull = function isFull() {
  */
 
 CoinSelector.prototype.isSpendable = function isSpendable(coin) {
-  var height = this.height;
   var maturity = constants.tx.COINBASE_MATURITY;
   var conf;
 
-  if (!(height >= 0))
+  if (this.height === -1)
     return true;
 
   if (this.confirmations > 0) {
     if (coin.height === -1)
       return this.confirmations <= 0;
 
-    conf = height - coin.height;
+    conf = this.height - coin.height;
 
     if (conf < 0)
       return false;
@@ -1549,7 +1642,7 @@ CoinSelector.prototype.isSpendable = function isSpendable(coin) {
   }
 
   if (coin.coinbase) {
-    if (height + 1 < coin.height + maturity)
+    if (this.height + 1 < coin.height + maturity)
       return false;
   }
 
@@ -1596,7 +1689,7 @@ CoinSelector.prototype.fund = function fund() {
     this.tx.addInput(coin);
     this.chosen.push(coin);
 
-    if (this.type === 'all')
+    if (this.selection === 'all')
       continue;
 
     // Stop once we're full.
@@ -1614,7 +1707,7 @@ CoinSelector.prototype.fund = function fund() {
 CoinSelector.prototype.select = function select(coins) {
   this.init(coins);
 
-  if (this.hardFee != null)
+  if (this.hardFee !== -1)
     this.selectHard(this.hardFee);
   else
     this.selectEstimate(constants.tx.MIN_FEE);
@@ -1658,7 +1751,7 @@ CoinSelector.prototype.selectEstimate = function selectEstimate(fee) {
     value: 0
   });
 
-  if (this.free && this.height >= 0) {
+  if (this.free && this.height !== -1) {
     size = this.tx.maxSize(this);
 
     // Note that this will only work
@@ -1678,7 +1771,7 @@ CoinSelector.prototype.selectEstimate = function selectEstimate(fee) {
 
     this.fee = this.getFee(size);
 
-    if (this.maxFee && this.fee > this.maxFee) {
+    if (this.maxFee > 0 && this.fee > this.maxFee) {
       throw new FundingError(
         'Fee is too high.',
         this.tx.getInputValue(),
diff --git a/lib/wallet/wallet.js b/lib/wallet/wallet.js
index c6abe1e1..71a18ccc 100644
--- a/lib/wallet/wallet.js
+++ b/lib/wallet/wallet.js
@@ -965,9 +965,9 @@ Wallet.prototype.fund = function fund(tx, options, callback, force) {
 
       try {
         tx.fund(coins, {
-          selection: options.selection || 'age',
+          selection: options.selection,
           round: options.round,
-          confirmed: options.confirmed,
+          confirmations: options.confirmations,
           free: options.free,
           hardFee: options.hardFee,
           subtractFee: options.subtractFee,