diff --git a/lib/script_interpreter.js b/lib/script_interpreter.js
index 2a34de781..a7de7d603 100644
--- a/lib/script_interpreter.js
+++ b/lib/script_interpreter.js
@@ -1,5 +1,7 @@
 'use strict';
 
+var _ = require('lodash');
+
 var Script = require('./script');
 var Opcode = require('./opcode');
 var BN = require('./crypto/bn');
@@ -8,6 +10,7 @@ var BufferReader = require('./encoding/bufferreader');
 var BufferWriter = require('./encoding/bufferwriter');
 var Signature = require('./crypto/signature');
 var PublicKey = require('./publickey');
+var Transaction = require('./transaction');
 
 /**
  * Bitcoin transactions contain scripts. Each input has a script called the
@@ -198,7 +201,7 @@ ScriptInterpreter.prototype.step = function() {
   var fRequireMinimal = (this.flags & ScriptInterpreter.SCRIPT_VERIFY_MINIMALDATA) != 0;
 
   //bool fExec = !count(vfExec.begin(), vfExec.end(), false);
-  var fExec = !(this.vfExec.indexOf(false) + 1);
+  var fExec = (this.vfExec.indexOf(false) !== -1);
 
   //
   // Read instruction
@@ -206,9 +209,8 @@ ScriptInterpreter.prototype.step = function() {
   var chunk = this.script.chunks[this.pc];
   this.pc++;
   var opcodenum = chunk.opcodenum;
-  if (typeof opcodenum === 'undefined') {
-    this.errstr = 'SCRIPT_ERR_BAD_OPCODE';
-    return false;
+  if (_.isUndefined(opcodenum)) {
+    opcodenum = chunk;
   }
   if (chunk.buf && chunk.buf.length > ScriptInterpreter.MAX_SCRIPT_ELEMENT_SIZE) {
     this.errstr = 'SCRIPT_ERR_PUSH_SIZE';
@@ -1016,7 +1018,6 @@ ScriptInterpreter.prototype.step = function() {
           }
           this.stack.pop();
 
-          // stack.push_back(fSuccess ? vchTrue : vchFalse);
           this.stack.push(fSuccess ? ScriptInterpreter.true : ScriptInterpreter.false);
 
           if (opcodenum === Opcode.OP_CHECKMULTISIGVERIFY) {
@@ -1042,6 +1043,12 @@ ScriptInterpreter.prototype.step = function() {
  * Translated from bitcoind's VerifyScript
  */
 ScriptInterpreter.prototype.verify = function(scriptSig, scriptPubkey, tx, nin, flags) {
+  if (_.isUndefined(tx)) {
+    tx = new Transaction();
+  }
+  if (_.isUndefined(nin)) {
+    nin = 0;
+  }
   this.set({
     script: scriptSig,
     tx: tx,
diff --git a/test/script_interpreter.js b/test/script_interpreter.js
index 28147da68..f12c34263 100644
--- a/test/script_interpreter.js
+++ b/test/script_interpreter.js
@@ -54,24 +54,28 @@ describe('ScriptInterpreter', function() {
 
   describe('#verify', function() {
 
-    it('should verify or unverify these trivial scripts from script_valid.json', function() {
-      var verified = ScriptInterpreter().verify(Script('OP_1'), Script('OP_1'), Transaction(), 0);
+    it('should verify these trivial scripts', function() {
+      var verified;
+      var si = ScriptInterpreter();
+      verified = si.verify(Script('OP_1'), Script('OP_1'));
+      console.log(si.errstr);
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('OP_1'), Script('OP_0'), Transaction(), 0);
+      var 
+      verified = ScriptInterpreter().verify(Script('OP_1'), Script('OP_0'));
       verified.should.equal(false);
-      verified = ScriptInterpreter().verify(Script('OP_0'), Script('OP_1'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('OP_0'), Script('OP_1'));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('OP_CODESEPARATOR'), Script('OP_1'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('OP_CODESEPARATOR'), Script('OP_1'));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script(''), Script('OP_DEPTH OP_0 OP_EQUAL'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script(''), Script('OP_DEPTH OP_0 OP_EQUAL'));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('OP_1 OP_2'), Script('OP_2 OP_EQUALVERIFY OP_1 OP_EQUAL'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('OP_1 OP_2'), Script('OP_2 OP_EQUALVERIFY OP_1 OP_EQUAL'));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('9 0x000000000000000010'), Script(''), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('9 0x000000000000000010'), Script(''));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('OP_1'), Script('OP_15 OP_ADD OP_16 OP_EQUAL'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('OP_1'), Script('OP_15 OP_ADD OP_16 OP_EQUAL'));
       verified.should.equal(true);
-      verified = ScriptInterpreter().verify(Script('OP_0'), Script('OP_IF OP_VER OP_ELSE OP_1 OP_ENDIF'), Transaction(), 0);
+      verified = ScriptInterpreter().verify(Script('OP_0'), Script('OP_IF OP_VER OP_ELSE OP_1 OP_ENDIF'));
       verified.should.equal(true);
     });