diff --git a/www/common/common-util.js b/www/common/common-util.js
index f5ba9a61c..e62ed7016 100644
--- a/www/common/common-util.js
+++ b/www/common/common-util.js
@@ -21,7 +21,7 @@ define([], function () {
             .replace(/ +$/, "")
             .split(" ");
         var byteString = String.fromCharCode.apply(null, hexArray);
-        return window.btoa(byteString).replace(/\//g, '-').slice(0,-2);
+        return window.btoa(byteString).replace(/\//g, '-').replace(/=+$/, '');
     };
 
     Util.base64ToHex = function (b64String) {