diff --git a/lib/script_interpreter.js b/lib/script_interpreter.js
index 952fc9b41..0c900e874 100644
--- a/lib/script_interpreter.js
+++ b/lib/script_interpreter.js
@@ -883,7 +883,6 @@ ScriptInterpreter.prototype.step = function() {
           subscript.findAndDelete(tmpScript);
 
           if (!this.checkSignatureEncoding(bufSig) || !this.checkPubkeyEncoding(bufPubkey)) {
-            // serror is set
             return false;
           }
 
@@ -973,7 +972,6 @@ ScriptInterpreter.prototype.step = function() {
             var bufPubkey = this.stack[this.stack.length - ikey];
 
             if (!this.checkSignatureEncoding(bufSig) || !this.checkPubkeyEncoding(bufPubkey)) {
-              // serror is set
               return false;
             }
 
@@ -1045,6 +1043,16 @@ ScriptInterpreter.prototype.step = function() {
 }
 
 /**
+ * Verifies a Script by executing it and returns true if it is valid.
+ * This function needs to be provided with the scriptSig and the scriptPubkey
+ * separately.
+ * @param {Script} scriptSig - the script's first part (corresponding to the tx input)
+ * @param {Script} scriptPubkey - the script's last part (corresponding to the tx output)
+ * @param {Transaction} [tx] - the Transaction containing the scriptSig in one input (used
+ *    to check signature validity for some opcodes like OP_CHECKSIG)
+ * @param {number} nin - index of the transaction input containing the scriptSig verified.
+ * @param {number} flags - evaluation flags. See ScriptInterpreter.SCRIPT_* constants
+ *
  * Translated from bitcoind's VerifyScript
  */
 ScriptInterpreter.prototype.verify = function(scriptSig, scriptPubkey, tx, nin, flags) {
@@ -1054,6 +1062,9 @@ ScriptInterpreter.prototype.verify = function(scriptSig, scriptPubkey, tx, nin,
   if (_.isUndefined(nin)) {
     nin = 0;
   }
+  if (_.isUndefined(flags)) {
+    flags = 0;
+  }
   this.set({
     script: scriptSig,
     tx: tx,
@@ -1128,7 +1139,6 @@ ScriptInterpreter.prototype.verify = function(scriptSig, scriptPubkey, tx, nin,
 
     // evaluate redeemScript
     if (!this.evaluate())
-    // serror is set
       return false;
 
     if (stackCopy.length === 0) {
diff --git a/lib/transaction/sighash.js b/lib/transaction/sighash.js
index 0d2782f22..30ebf6f06 100644
--- a/lib/transaction/sighash.js
+++ b/lib/transaction/sighash.js
@@ -11,6 +11,7 @@ var BN = require('../crypto/bn');
 var Hash = require('../crypto/hash');
 var ECDSA = require('../crypto/ecdsa');
 var $ = require('../util/preconditions');
+var _ = require('lodash');
 
 var SIGHASH_SINGLE_BUG = '0000000000000000000000000000000000000000000000000000000000000001';
 var BITS_64_ON = 'ffffffffffffffff';
@@ -122,8 +123,8 @@ function sign(transaction, privateKey, sighashType, inputIndex, subscript) {
  * @return {boolean}
  */
 function verify(transaction, signature, publicKey, inputIndex, subscript) {
-  $.checkArgument(transaction);
-  $.checkArgument(signature && signature.nhashtype);
+  $.checkArgument(!_.isUndefined(transaction));
+  $.checkArgument(!_.isUndefined(signature) && !_.isUndefined(signature.nhashtype));
   var hashbuf = sighash(transaction, signature.nhashtype, inputIndex, subscript);
   return ECDSA.verify(hashbuf, signature, publicKey, 'little');
 }
diff --git a/test/script_interpreter.js b/test/script_interpreter.js
index 91220b1cc..88586dbbc 100644
--- a/test/script_interpreter.js
+++ b/test/script_interpreter.js
@@ -202,7 +202,7 @@ describe('ScriptInterpreter', function() {
     var verified = interp.verify(scriptSig, scriptPubkey, spendtx, 0, flags);
     verified.should.equal(expected);
   };
-  describe('bitcoind fixtures', function() {
+  describe('bitcoind script evaluation fixtures', function() {
     var testAllFixtures = function(set, expected) {
       var c = 0;
       set.forEach(function(vector) {
@@ -221,13 +221,15 @@ describe('ScriptInterpreter', function() {
     testAllFixtures(script_valid, true);
     testAllFixtures(script_invalid, false);
 
+  });
+  describe('bitcoind transaction evaluation fixtures', function() {
     var c = 0;
     tx_valid.forEach(function(vector) {
       if (vector.length === 1) {
         return;
       }
       c++;
-      it.skip('should pass tx_valid vector ' + c, function() {
+      it('should pass tx_valid vector ' + c, function() {
         var inputs = vector[0];
         var txhex = vector[1];
         var flags = getFlags(vector[2]);
@@ -240,8 +242,7 @@ describe('ScriptInterpreter', function() {
           if (txoutnum === -1) {
             txoutnum = 0xffffffff; //bitcoind casts -1 to an unsigned int
           }
-          var txkey = txid + ':' + txoutnum;
-          map[txkey] = Script.fromBitcoindString(scriptPubKeyStr);
+          map[txid + ':' + txoutnum] = Script.fromBitcoindString(scriptPubKeyStr);
         });
 
         var tx = Transaction(txhex);
@@ -249,9 +250,9 @@ describe('ScriptInterpreter', function() {
           var scriptSig = txin.script;
           var txidhex = txin.prevTxId.toString('hex');
           var txoutnum = txin.outputIndex;
-          var txkey = txidhex + ':' + txoutnum;
-          var scriptPubkey = map[txkey];
+          var scriptPubkey = map[txidhex + ':' + txoutnum];
           should.exist(scriptPubkey);
+          should.exist(scriptSig);
           var interp = ScriptInterpreter();
           var verified = interp.verify(scriptSig, scriptPubkey, tx, j, flags);
           verified.should.equal(true);