diff --git a/Script.js b/Script.js
index 4c2aa49..4e89d9e 100644
--- a/Script.js
+++ b/Script.js
@@ -118,8 +118,8 @@ function spec(b) {
   {
     return (this.chunks.length > 3 &&
     	    isSmallIntOp(this.chunks[0]) &&
-    	    isSmallIntOp(this.chunks[-2]) &&
-	    this.chunks[-1] == OP_CHECKMULTISIG);
+    	    isSmallIntOp(this.chunks[this.chunks.length-2]) &&
+	    this.chunks[this.chunks.length-1] == OP_CHECKMULTISIG);
   };
 
   // is this a script form we know?
@@ -443,7 +443,7 @@ function spec(b) {
   };
 
   Script.chunksToBuffer = function (chunks) {
-    var buf = Put();
+    var buf = new Put();
     for (var i = 0, l = chunks.length; i < l; i++) {
       var data = chunks[i];
       if (Buffer.isBuffer(data)) {