diff --git a/browser/base/content/browser-ctrlTab.js b/browser/base/content/browser-ctrlTab.js
index 8191cb6873f..c2b6a315604 100644
--- a/browser/base/content/browser-ctrlTab.js
+++ b/browser/base/content/browser-ctrlTab.js
@@ -399,9 +399,9 @@ var ctrlTab = {
   suspendGUI: function ctrlTab_suspendGUI() {
     document.removeEventListener("keyup", this, true);
 
-    Array.forEach(this.previews, function (preview) {
+    for (let preview of this.previews) {
       this.updatePreview(preview, null);
-    }, this);
+    }
   },
 
   onKeyPress: function ctrlTab_onKeyPress(event) {