diff --git a/lib/transaction/transaction.js b/lib/transaction/transaction.js
index 46983ad..693e97f 100644
--- a/lib/transaction/transaction.js
+++ b/lib/transaction/transaction.js
@@ -191,9 +191,10 @@ Transaction.prototype.invalidSatoshis = function() {
 Transaction.prototype.getSerializationError = function(opts) {
   opts = opts || {};
 
+  var unspent = this._getUnspentValue();
   return this._isInvalidSatoshis() ||
-      this._hasMoreOutputThanInput(opts) ||
-      this._hasFeeError(opts) ||
+      this._hasMoreOutputThanInput(opts, unspent) ||
+      this._hasFeeError(opts, unspent) ||
       this._hasDustOutputs(opts) ||
       this._isMissingSignatures(opts);
 };
@@ -204,31 +205,28 @@ Transaction.prototype._isInvalidSatoshis = function() {
   }
 };
 
-Transaction.prototype._hasFeeError = function(opts) {
-  if (this._getUnspentValue() < 0) {
+Transaction.prototype._hasFeeError = function(opts, unspent) {
+  if (unspent < 0) {
     // The concept of a fee is meaningless when the unspent output value is negative.
     return;
   }
-  return this._isFeeDifferent() ||
-      this._isFeeTooLarge(opts) ||
-      this._isFeeTooSmall(opts);
+  return this._isFeeDifferent(unspent) ||
+      this._isFeeTooLarge(opts, unspent) ||
+      this._isFeeTooSmall(opts, unspent);
 };
 
-Transaction.prototype._isFeeDifferent = function() {
-  if (!_.isUndefined(this._fee)) {
-    var fee = this._fee;
-    var unspent = this._getUnspentValue();
-    if (fee !== unspent) {
-      return new errors.Transaction.FeeError.Different('Unspent value is ' + unspent + ' but specified fee is ' + fee);
-    }
+Transaction.prototype._isFeeDifferent = function(unspent) {
+  if (!_.isUndefined(this._fee) && this._fee !== unspent) {
+    return new errors.Transaction.FeeError.Different(
+      'Unspent value is ' + unspent + ' but specified fee is ' + this._fee
+    );
   }
 };
 
-Transaction.prototype._isFeeTooLarge = function(opts) {
+Transaction.prototype._isFeeTooLarge = function(opts, fee) {
   if (opts.disableLargeFees) {
     return;
   }
-  var fee = this._getUnspentValue();
   var maximumFee = Math.floor(Transaction.FEE_SECURITY_MARGIN * this._estimateFee());
   if (fee > maximumFee) {
     if (this._missingChange()) {
@@ -238,11 +236,10 @@ Transaction.prototype._isFeeTooLarge = function(opts) {
   }
 };
 
-Transaction.prototype._isFeeTooSmall = function(opts) {
+Transaction.prototype._isFeeTooSmall = function(opts, fee) {
   if (opts.disableSmallFees) {
     return;
   }
-  var fee = this._getUnspentValue();
   var minimumFee = Math.ceil(this._estimateFee() / Transaction.FEE_SECURITY_MARGIN);
   if (fee < minimumFee) {
     return new errors.Transaction.FeeError.TooSmall('expected more than ' + minimumFee + ' but got ' + fee);
@@ -275,11 +272,11 @@ Transaction.prototype._isMissingSignatures = function(opts) {
   }
 };
 
-Transaction.prototype._hasMoreOutputThanInput = function(opts) {
+Transaction.prototype._hasMoreOutputThanInput = function(opts, unspent) {
   if (opts.disableMoreOutputThanInput) {
     return;
   }
-  if (this._getUnspentValue() < 0) {
+  if (unspent < 0) {
     return new errors.Transaction.InvalidOutputAmountSum();
   }
 };