diff --git a/src/plugins/GreaseMonkey/data/values.js b/src/plugins/GreaseMonkey/data/values.js
index 637c288dd..e7e6d70b2 100644
--- a/src/plugins/GreaseMonkey/data/values.js
+++ b/src/plugins/GreaseMonkey/data/values.js
@@ -13,13 +13,11 @@ function GM_getValue(aKey, aDefault) {
 }
 
 function GM_listValues() {
-    var prefixLen = "%1".length;
     var values = [];
-    var i = 0;
     for (var i = 0; i < localStorage.length; i++) {
         var k = localStorage.key(i);
-        if (k.substr(0, prefixLen) === "%1") {
-            values.push(k.substr(prefixLen));
+        if (k.indexOf("%1") === 0) {
+            values.push(k.replace("%1", ""));
         }
     }
     return values;
diff --git a/src/plugins/GreaseMonkey/data/values.min.js b/src/plugins/GreaseMonkey/data/values.min.js
index d10c11965..2ebaffbcd 100644
--- a/src/plugins/GreaseMonkey/data/values.min.js
+++ b/src/plugins/GreaseMonkey/data/values.min.js
@@ -1 +1 @@
-function GM_deleteValue(b){localStorage.removeItem("%1"+b)}function GM_getValue(b,a){var c=localStorage.getItem("%1"+b);return null===c&&"undefined"!=typeof a?a:c}function GM_listValues(){for(var b=[],a=0,a=0;a<localStorage.length;a++){var c=localStorage.key(a);"%1"===c.substr(0,2)&&b.push(c.substr(2))}return b}function GM_setValue(b,a){localStorage.setItem("%1"+b,a)};
+function GM_deleteValue(a){localStorage.removeItem("%1"+a)}function GM_getValue(a,b){var c=localStorage.getItem("%1"+a);return null===c&&"undefined"!=typeof b?b:c}function GM_listValues(){for(var a=[],b=0;b<localStorage.length;b++){var c=localStorage.key(b);0===c.indexOf("%1")&&a.push(c.replace("%1",""))}return a}function GM_setValue(a,b){localStorage.setItem("%1"+a,b)};