diff -u b/core/lib/Drupal/Core/HtmlPageController.php b/core/lib/Drupal/Core/HtmlPageController.php
--- b/core/lib/Drupal/Core/HtmlPageController.php
+++ b/core/lib/Drupal/Core/HtmlPageController.php
@@ -52,7 +52,7 @@
     // require an _internal route.  For examples, see:
     // https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing/internal.xml
     // https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Controller/InternalController.php
-    $attributes = clone($request->attributes);
+    $attributes = clone $request->attributes;
     $controller = $_content;
 
     // We need to clean off the derived information and such so that the