diff --git a/core/modules/node/lib/Drupal/node/NodeFormController.php b/core/modules/node/lib/Drupal/node/NodeFormController.php
index 0c6bd14..045f3d6 100644
--- a/core/modules/node/lib/Drupal/node/NodeFormController.php
+++ b/core/modules/node/lib/Drupal/node/NodeFormController.php
@@ -269,7 +269,9 @@ protected function actionsElement(array $form, array &$form_state) {
 
     // Add an additional button_type attribute to the preview button so that
     // themes / modules can target it more easily.
-    $element['preview']['#button_type'] = 'preview';
+    // @todo Update this line if/once arbitrary button types are supported.
+    // @see http://drupal.org/node/1238484
+    // $element['preview']['#button_type'] = 'preview';
 
     return $element;
   }