diff --git a/core/tests/Drupal/Tests/Core/Theme/TwigEngineTest.php b/core/tests/Drupal/Tests/Core/Theme/TwigEngineTest.php
index baf45c1..d32e2d5 100644
--- a/core/tests/Drupal/Tests/Core/Theme/TwigEngineTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/TwigEngineTest.php
@@ -31,7 +31,7 @@ protected function setUp() {
 
     // Ensure that twig.engine is loaded, it is needed to access
     // twig_drupal_escape_filter().
-    require_once $this->root . '/core/themes/engines/twig/twig.engine';
+    require_once $this->root . '/core/themes/engines/twig/twig.engine.php';
 
     $this->twigEnvironment = $this->getMock('\Twig_Environment');
   }