diff --git a/lib/javascript-static.js b/lib/javascript-static.js
index ef41865c84f..92150820e54 100644
--- a/lib/javascript-static.js
+++ b/lib/javascript-static.js
@@ -704,9 +704,7 @@ YUI.add('moodle-core-io', function(Y) {
  * @return  {Number}    Number of pending items remaining after removing this item
  */
 M.util.js_complete = function(uniqid) {
-    // Use the Y.Array.indexOf instead of the native because some older browsers do not support
-    // the native function. Y.Array polyfills the native function if it does not exist.
-    var index = Y.Array.indexOf(M.util.pending_js, uniqid);
+    const index = M.util.pending_js.indexOf(uniqid);
     if (index >= 0) {
         M.util.complete_js.push(M.util.pending_js.splice(index, 1)[0]);
     } else {