diff --git a/core/modules/system/tests/modules/ajax_forms_test/ajax_forms_test.module b/core/modules/system/tests/modules/ajax_forms_test/ajax_forms_test.module
index 3bbf028..733f1dc 100644
--- a/core/modules/system/tests/modules/ajax_forms_test/ajax_forms_test.module
+++ b/core/modules/system/tests/modules/ajax_forms_test/ajax_forms_test.module
@@ -556,7 +556,7 @@ function ajax_forms_test_lazy_load_form_submit($form, &$form_state) {
   if ($form_state['values']['add_files']) {
     $path = drupal_get_path('module', 'system');
     $attached = array(
-      $form['#attached'] = array(
+      '#attached' => array(
         'css' => array(
           $path . '/css/system.admin.css' => array(),
         ),