diff -u b/core/modules/ckeditor/src/Tests/CKEditorTest.php b/core/modules/ckeditor/src/Tests/CKEditorTest.php
--- b/core/modules/ckeditor/src/Tests/CKEditorTest.php
+++ b/core/modules/ckeditor/src/Tests/CKEditorTest.php
@@ -432,7 +432,6 @@
     return array(
       file_create_url('core/modules/ckeditor/css/ckeditor-iframe.css'),
       file_create_url('core/modules/system/css/system.module.css'),
-      file_create_url('core/modules/ckeditor/css/plugins/language/ckeditor.language.css'),
     );
   }
 
@@ -441,6 +440,7 @@
     return array(
       file_create_url('core/modules/ckeditor/css/ckeditor-iframe.css'),
       file_create_url('core/modules/system/css/system.module.css'),
+      file_create_url('core/modules/ckeditor/css/plugins/language/ckeditor.language.css'),
     );
   }