diff --git a/lib/ScriptInterpreter.js b/lib/ScriptInterpreter.js
index db131da28..a22c29e68 100644
--- a/lib/ScriptInterpreter.js
+++ b/lib/ScriptInterpreter.js
@@ -242,7 +242,7 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
 
           case Opcode.map.OP_DEPTH:
             // -- stacksize
-            var value = new bignum(this.stack.length);
+            var value = bignum(this.stack.length);
             this.stack.push(intToBufferSM(value));
             break;
 
@@ -351,7 +351,7 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
 
           case Opcode.map.OP_SIZE:
             // (in -- in size)
-            var value = new bignum(this.stackTop().length);
+            var value = bignum(this.stackTop().length);
             this.stack.push(intToBufferSM(value));
             break;
 
@@ -427,16 +427,16 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
             var num = bufferSMToInt(this.stackTop());
             switch (opcode) {
               case Opcode.map.OP_1ADD:
-                num = num.add(new bignum(1));
+                num = num.add(1);
                 break;
               case Opcode.map.OP_1SUB:
-                num = num.sub(new bignum(1));
+                num = num.sub(1);
                 break;
               case Opcode.map.OP_2MUL:
-                num = num.mul(new bignum(2));
+                num = num.mul(2);
                 break;
               case Opcode.map.OP_2DIV:
-                num = num.div(new bignum(2));
+                num = num.div(2);
                 break;
               case Opcode.map.OP_NEGATE:
                 num = num.neg();
@@ -445,10 +445,10 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
                 num = num.abs();
                 break;
               case Opcode.map.OP_NOT:
-                num = new bignum(num.cmp(new bignum(0)) == 0 ? 1 : 0);
+                num = bignum(num.cmp(0) == 0 ? 1 : 0);
                 break;
               case Opcode.map.OP_0NOTEQUAL:
-                num = new bignum(num.cmp(new bignum(0)) == 0 ? 0 : 1);
+                num = bignum(num.cmp(0) == 0 ? 0 : 1);
                 break;
             }
             this.stack[this.stack.length - 1] = intToBufferSM(num);
@@ -494,51 +494,51 @@ ScriptInterpreter.prototype.eval = function eval(script, tx, inIndex, hashType,
                 break;
 
               case Opcode.map.OP_LSHIFT:
-                if (v2.cmp(new bignum(0)) < 0 || v2.cmp(new bignum(2048)) > 0) {
+                if (v2.cmp(0) < 0 || v2.cmp(bignum(2048)) > 0) {
                   throw new Error("OP_LSHIFT parameter out of bounds");
                 }
                 num = v1.shiftLeft(v2);
                 break;
 
               case Opcode.map.OP_RSHIFT:
-                if (v2.cmp(new bignum(0)) < 0 || v2.cmp(new bignum(2048)) > 0) {
+                if (v2.cmp(0) < 0 || v2.cmp(bignum(2048)) > 0) {
                   throw new Error("OP_RSHIFT parameter out of bounds");
                 }
                 num = v1.shiftRight(v2);
                 break;
 
               case Opcode.map.OP_BOOLAND:
-                num = new bignum((v1.cmp(new bignum(0)) != 0 && v2.cmp(new bignum(0)) != 0) ? 1 : 0);
+                num = bignum((v1.cmp(0) != 0 && v2.cmp(0) != 0) ? 1 : 0);
                 break;
 
               case Opcode.map.OP_BOOLOR:
-                num = new bignum((v1.cmp(new bignum(0)) != 0 || v2.cmp(new bignum(0)) != 0) ? 1 : 0);
+                num = bignum((v1.cmp(0) != 0 || v2.cmp(0) != 0) ? 1 : 0);
                 break;
 
               case Opcode.map.OP_NUMEQUAL:
               case Opcode.map.OP_NUMEQUALVERIFY:
-                num = new bignum(v1.cmp(v2) == 0 ? 1 : 0);
+                num = bignum(v1.cmp(v2) == 0 ? 1 : 0);
                 break;
 
               case Opcode.map.OP_NUMNOTEQUAL:
                 ;
-                num = new bignum(v1.cmp(v2) != 0 ? 1 : 0);
+                num = bignum(v1.cmp(v2) != 0 ? 1 : 0);
                 break;
 
               case Opcode.map.OP_LESSTHAN:
-                num = new bignum(v1.lt(v2) ? 1 : 0);
+                num = bignum(v1.lt(v2) ? 1 : 0);
                 break;
 
               case Opcode.map.OP_GREATERTHAN:
-                num = new bignum(v1.gt(v2) ? 1 : 0);
+                num = bignum(v1.gt(v2) ? 1 : 0);
                 break;
 
               case Opcode.map.OP_LESSTHANOREQUAL:
-                num = new bignum(v1.gt(v2) ? 0 : 1);
+                num = bignum(v1.gt(v2) ? 0 : 1);
                 break;
 
               case Opcode.map.OP_GREATERTHANOREQUAL:
-                num = new bignum(v1.lt(v2) ? 0 : 1);
+                num = bignum(v1.lt(v2) ? 0 : 1);
                 break;
 
               case Opcode.map.OP_MIN:
@@ -835,7 +835,7 @@ ScriptInterpreter.prototype.getPrimitiveStack = function getPrimitiveStack() {
       return buffertools.toHex(chunk.slice(0));
     }
     var num = bufferSMToInt(chunk);
-    if (num.cmp(new bignum(-128)) >= 0 && num.cmp(new bignum(127)) <= 0) {
+    if (num.cmp(-128) >= 0 && num.cmp(127) <= 0) {
       return num.toNumber();
     } else {
       return buffertools.toHex(chunk.slice(0));