diff --git a/core/misc/vertical-tabs.js b/core/misc/vertical-tabs.js
index a381bdc..e284c93 100644
--- a/core/misc/vertical-tabs.js
+++ b/core/misc/vertical-tabs.js
@@ -29,8 +29,10 @@
    */
   Drupal.behaviors.verticalTabs = {
     attach: function (context) {
+      var width = drupalSettings.widthBreakpoint || 640;
+      var mq = '(max-width: ' + width + 'px)';
 
-      if (!Drupal.checkWidthBreakpoint()) {
+      if (window.matchMedia(mq).matches) {
         return;
       }
 
diff --git a/core/modules/ckeditor/js/ckeditor.js b/core/modules/ckeditor/js/ckeditor.js
index f67ed62..14e8094 100644
--- a/core/modules/ckeditor/js/ckeditor.js
+++ b/core/modules/ckeditor/js/ckeditor.js
@@ -223,7 +223,7 @@
       var classes = dialogSettings.dialogClass ? dialogSettings.dialogClass.split(' ') : [];
       classes.push('editor-dialog');
       dialogSettings.dialogClass = classes.join(' ');
-      dialogSettings.autoResize = Drupal.checkWidthBreakpoint(600);
+      dialogSettings.autoResize = window.matchMedia('(min-width: 600px)').matches;
 
       // Add a "Loading…" message, hide it underneath the CKEditor toolbar,
       // create a Drupal.Ajax instance to load the dialog and trigger it.