diff --git a/core/modules/system/tests/modules/dialog_test/js/dialog.debug.es6.js b/core/modules/system/tests/modules/dialog_test/js/dialog.debug.es6.js
index 1052dda901..5a69d67b5b 100644
--- a/core/modules/system/tests/modules/dialog_test/js/dialog.debug.es6.js
+++ b/core/modules/system/tests/modules/dialog_test/js/dialog.debug.es6.js
@@ -3,21 +3,17 @@
  *  Testing behavior for JSWebAssertTest.
  */
 
-(function ($, window, Drupal) {
-
-  'use strict';
-
+(($, window, Drupal) => {
   Drupal.dialog_debug = {
-    has_open_dialog: false
+    has_open_dialog: false,
   };
 
   // Register the dialog opened by listening to the dialogContentResize event.
-  $('#drupal-modal').on('dialogContentResize',  () => {
+  $('#drupal-modal').on('dialogContentResize', () => {
     Drupal.dialog_debug.has_open_dialog = true;
   });
   // Register the beforecreate and afterclose to indicate the dialog has been closed.
   $(window).on('dialog:beforecreate dialog:afterclose', () => {
     Drupal.dialog_debug.has_open_dialog = false;
   });
-
 })(jQuery, window, Drupal);
diff --git a/core/modules/system/tests/modules/dialog_test/js/dialog.debug.js b/core/modules/system/tests/modules/dialog_test/js/dialog.debug.js
index 7a25343365..cd192a738f 100644
--- a/core/modules/system/tests/modules/dialog_test/js/dialog.debug.js
+++ b/core/modules/system/tests/modules/dialog_test/js/dialog.debug.js
@@ -6,9 +6,6 @@
 **/
 
 (function ($, window, Drupal) {
-
-  'use strict';
-
   Drupal.dialog_debug = {
     has_open_dialog: false
   };