diff --git a/lib/main.js b/lib/main.js
index 95581c2be..5655a762e 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -223,6 +223,8 @@
             // Find termination
             var str = "";
             var i = 0, l = hex.length;
+            if (hex.substring(0, 2) == '0x')
+                i = 2;
             for(; i < l; i+=2) {
                 var code = hex.charCodeAt(i);
                 if(code === 0) {
@@ -244,7 +246,8 @@
             var hex = this.toHex(str);
             while(hex.length < pad*2)
                 hex += "00";
-            return hex;
+
+            return "0x" + hex;
         },
 
         eth: {