diff --git a/core/lib/Drupal/Core/Template/TwigTemplate.php b/core/lib/Drupal/Core/Template/TwigTemplate.php
index 8dfc424..cb2d91d 100644
--- a/core/lib/Drupal/Core/Template/TwigTemplate.php
+++ b/core/lib/Drupal/Core/Template/TwigTemplate.php
@@ -39,7 +39,7 @@
    * @return mixed
    *   The requested variable.
    */
-  protected function getContextReference(&$context, $item)
+  final protected function getContextReference(&$context, $item)
   {
     // Optimized version. NULL is a valid value for $context[$item], we only
     // want to error if it hasn't been defined at all.