diff --git a/core/lib/Drupal/Core/Render/Element/RenderElement.php b/core/lib/Drupal/Core/Render/Element/RenderElement.php
index bd30b47..30a31d0 100644
--- a/core/lib/Drupal/Core/Render/Element/RenderElement.php
+++ b/core/lib/Drupal/Core/Render/Element/RenderElement.php
@@ -227,18 +227,18 @@ public static function preRenderAjaxForm($element) {
 
       $settings = $element['#ajax'];
 
-      // Assign default settings. When 'path' is set to NULL, ajax.js submits the
+      // Assign default settings. When 'url' is set to NULL, ajax.js submits the
       // Ajax request to the same URL as the form or link destination is for
       // someone with JavaScript disabled. This is generally preferred as a way to
       // ensure consistent server processing for js and no-js users, and Drupal's
       // content negotiation takes care of formatting the response appropriately.
-      // However, 'path' and 'options' may be set when wanting server processing
+      // However, 'url' and 'options' may be set when wanting server processing
       // to be substantially different for a JavaScript triggered submission.
       // One such substantial difference is form elements that use
       // #ajax['callback'] for determining which part of the form needs
       // re-rendering. For that, we have a special 'system/ajax' route.
       $settings += array(
-        'path' => isset($settings['callback']) ? 'system/ajax' : NULL,
+        'url' => isset($settings['callback']) ? Url::fromRoute('system.ajax') : NULL,
         'options' => array(),
         'accepts' => 'application/vnd.drupal-ajax'
       );