diff --git a/include/util.js b/include/util.js
index 05c1ac32..0e94537c 100644
--- a/include/util.js
+++ b/include/util.js
@@ -21,17 +21,21 @@ var Util = {};
 Array.prototype.push8 = function (num) {
     this.push(num & 0xFF);
 };
+Object.defineProperty(Array.prototype, 'push8', {enumerable: false});
 
 Array.prototype.push16 = function (num) {
     this.push((num >> 8) & 0xFF,
               (num     ) & 0xFF  );
 };
+Object.defineProperty(Array.prototype, 'push16', {enumerable: false});
+
 Array.prototype.push32 = function (num) {
     this.push((num >> 24) & 0xFF,
               (num >> 16) & 0xFF,
               (num >>  8) & 0xFF,
               (num      ) & 0xFF  );
 };
+Object.defineProperty(Array.prototype, 'push32', {enumerable: false});
 
 // IE does not support map (even in IE9)
 //This prototype is provided by the Mozilla foundation and