diff --git a/lib/transaction/transaction.js b/lib/transaction/transaction.js
index 6d1feb6..232dafe 100644
--- a/lib/transaction/transaction.js
+++ b/lib/transaction/transaction.js
@@ -191,57 +191,54 @@ Transaction.prototype.invalidSatoshis = function() {
 Transaction.prototype.getSerializationError = function(opts) {
   opts = opts || {};
 
-  return this._isInvalidSatoshis() ||
-      this._hasFeeError(opts) ||
-      this._hasDustOutputs(opts) ||
-      this._isMissingSignatures(opts) ||
-      this._hasMoreOutputThanInput(opts);
-};
-
-Transaction.prototype._isInvalidSatoshis = function() {
   if (this.invalidSatoshis()) {
     return new errors.Transaction.InvalidSatoshis();
   }
+
+  var unspent = this._getUnspentValue();
+  var unspentError;
+  if (unspent < 0) {
+    if (!opts.disableMoreOutputThanInput) {
+      unspentError = new errors.Transaction.InvalidOutputAmountSum();
+    }
+  } else {
+    unspentError = this._hasFeeError(opts, unspent);
+  }
+
+  return  unspentError ||
+    this._hasDustOutputs(opts) ||
+    this._isMissingSignatures(opts);
 };
 
-Transaction.prototype._hasFeeError = function(opts) {
-  return this._isFeeDifferent() ||
-      this._isFeeTooLarge(opts) ||
-      this._isFeeTooSmall(opts);
-};
+Transaction.prototype._hasFeeError = function(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);
+  if (!_.isUndefined(this._fee) && this._fee !== unspent) {
+    return new errors.Transaction.FeeError.Different(
+      'Unspent value is ' + unspent + ' but specified fee is ' + this._fee
+    );
+  }
+
+  if (!opts.disableLargeFees) {
+    var maximumFee = Math.floor(Transaction.FEE_SECURITY_MARGIN * this._estimateFee());
+    if (unspent > maximumFee) {
+      if (this._missingChange()) {
+        return new errors.Transaction.ChangeAddressMissing(
+          'Fee is too large and no change address was provided'
+        );
+      }
+      return new errors.Transaction.FeeError.TooLarge(
+        'expected less than ' + maximumFee + ' but got ' + unspent
+      );
     }
   }
-};
 
-Transaction.prototype._isFeeTooLarge = function(opts) {
-  if (opts.disableLargeFees) {
-    return;
-  }
-  var fee = this._getUnspentValue();
-  var maximumFee = Math.floor(Transaction.FEE_SECURITY_MARGIN * this._estimateFee());
-  if (fee > maximumFee) {
-    if (this._missingChange()) {
-      return new errors.Transaction.ChangeAddressMissing('Fee is too large and no change address was provided');
+  if (!opts.disableSmallFees) {
+    var minimumFee = Math.ceil(this._estimateFee() / Transaction.FEE_SECURITY_MARGIN);
+    if (unspent < minimumFee) {
+      return new errors.Transaction.FeeError.TooSmall(
+        'expected more than ' + minimumFee + ' but got ' + unspent
+      );
     }
-    return new errors.Transaction.FeeError.TooLarge('expected less than ' + maximumFee + ' but got ' + fee);
-  }
-};
-
-Transaction.prototype._isFeeTooSmall = function(opts) {
-  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);
   }
 };
 
@@ -271,15 +268,6 @@ Transaction.prototype._isMissingSignatures = function(opts) {
   }
 };
 
-Transaction.prototype._hasMoreOutputThanInput = function(opts) {
-  if (opts.disableMoreOutputThanInput) {
-    return;
-  }
-  if (this._getUnspentValue() < 0) {
-    return new errors.Transaction.InvalidOutputAmountSum();
-  }
-};
-
 Transaction.prototype.inspect = function() {
   return '<Transaction: ' + this.uncheckedSerialize() + '>';
 };
diff --git a/test/transaction/transaction.js b/test/transaction/transaction.js
index 66db3e5..77ae014 100644
--- a/test/transaction/transaction.js
+++ b/test/transaction/transaction.js
@@ -385,8 +385,32 @@ describe('Transaction', function() {
         return transaction.serialize();
       }).to.throw(errors.Transaction.FeeError.Different);
     });
+    it('checks output amount before fee errors', function() {
+      var transaction = new Transaction();
+      transaction.from(simpleUtxoWith1BTC);
+      transaction
+        .to(toAddress, 10000000000000)
+        .change(changeAddress)
+        .fee(5);
+
+      expect(function() {
+        return transaction.serialize();
+      }).to.throw(errors.Transaction.InvalidOutputAmountSum);
+    });
+    it('will throw fee error with disableMoreOutputThanInput enabled (but not triggered)', function() {
+      var transaction = new Transaction();
+      transaction.from(simpleUtxoWith1BTC);
+      transaction
+        .to(toAddress, 90000000)
+        .change(changeAddress)
+        .fee(10000000);
+
+      expect(function() {
+        return transaction.serialize({disableMoreOutputThanInput: true});
+      }).to.throw(errors.Transaction.FeeError.TooLarge);
+    });
     describe('skipping checks', function() {
-      var buildSkipTest = function(builder, check) {
+      var buildSkipTest = function(builder, check, expectedError) {
         return function() {
           var transaction = new Transaction();
           transaction.from(simpleUtxoWith1BTC);
@@ -400,7 +424,7 @@ describe('Transaction', function() {
           }).not.to.throw();
           expect(function() {
             return transaction.serialize();
-          }).to.throw();
+          }).to.throw(expectedError);
         };
       };
       it('can skip the check for too much fee', buildSkipTest(
@@ -409,54 +433,39 @@ describe('Transaction', function() {
             .fee(50000000)
             .change(changeAddress)
             .sign(privateKey);
-        }, 'disableLargeFees'));
+        }, 'disableLargeFees', errors.Transaction.FeeError.TooLarge
+      ));
       it('can skip the check for a fee that is too small', buildSkipTest(
         function(transaction) {
           return transaction
             .fee(1)
             .change(changeAddress)
             .sign(privateKey);
-        }, 'disableSmallFees'));
+        }, 'disableSmallFees', errors.Transaction.FeeError.TooSmall
+      ));
       it('can skip the check that prevents dust outputs', buildSkipTest(
         function(transaction) {
           return transaction
             .to(toAddress, 100)
             .change(changeAddress)
             .sign(privateKey);
-        }, 'disableDustOutputs'));
-      it('can skip the check that prevents unsigned outputs', function() {
-        var transaction = new Transaction();
-        transaction.from(simpleUtxoWith1BTC);
-        transaction.to(toAddress, 10000);
-        transaction.change(changeAddress);
-        var options = {};
-        options.disableIsFullySigned = true;
-        expect(function() {
-          return transaction.serialize(options);
-        }).not.to.throw(errors.Transaction.MissingSignatures);
-        expect(function() {
-          return transaction.serialize();
-        }).to.throw(errors.Transaction.MissingSignatures);
-      });
-      it('can skip the check that avoids spending more bitcoins than the inputs for a transaction', function() {
-        var transaction = new Transaction();
-        transaction.from(simpleUtxoWith1BTC);
-        transaction.to(toAddress, 10000000000000);
-        transaction.change(changeAddress);
-        expect(function() {
-          return transaction.serialize({
-            disableSmallFees: true,
-            disableIsFullySigned: true,
-            disableMoreOutputThanInput: true
-          });
-        }).not.to.throw(errors.Transaction.InvalidOutputAmountSum);
-        expect(function() {
-          return transaction.serialize({
-            disableIsFullySigned: true,
-            disableSmallFees: true
-          });
-        }).to.throw(errors.Transaction.InvalidOutputAmountSum);
-      });
+        }, 'disableDustOutputs', errors.Transaction.DustOutputs
+      ));
+      it('can skip the check that prevents unsigned outputs', buildSkipTest(
+        function(transaction) {
+          return transaction
+            .to(toAddress, 10000)
+            .change(changeAddress);
+        }, 'disableIsFullySigned', errors.Transaction.MissingSignatures
+      ));
+      it('can skip the check that avoids spending more bitcoins than the inputs for a transaction', buildSkipTest(
+        function(transaction) {
+          return transaction
+            .to(toAddress, 10000000000000)
+            .change(changeAddress)
+            .sign(privateKey);
+        }, 'disableMoreOutputThanInput', errors.Transaction.InvalidOutputAmountSum
+      ));
     });
   });
 
@@ -511,6 +520,23 @@ describe('Transaction', function() {
 
     });
 
+    it('not if has null input (and not coinbase)', function() {
+
+      var tx = new Transaction()
+        .from({
+          'txId': testPrevTx,
+          'outputIndex': 0,
+          'script': testScript,
+          'satoshis': testAmount
+        }).to('mrU9pEmAx26HcbKVrABvgL7AwA5fjNFoDc', testAmount - 10000);
+
+      tx.isCoinbase = sinon.stub().returns(false);
+      tx.inputs[0].isNull = sinon.stub().returns(true);
+      var verify = tx.verify();
+      verify.should.equal('transaction input 0 has null input');
+
+    });
+
   });
 
   describe('to and from JSON', function() {