diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigSettingsTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigSettingsTest.php
index 4fd4417..c59c99b 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigSettingsTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigSettingsTest.php
@@ -76,6 +76,7 @@ function testTwigDebugOverride() {
    * Ensures Twig template cache setting can be overridden.
    */
   function testTwigCacheOverride() {
+    $extension = twig_extension();
     theme_enable(array('test_theme_twig'));
     variable_set('theme_default', 'test_theme_twig');
 
@@ -86,11 +87,11 @@ function testTwigCacheOverride() {
     }
 
     // Load array of Twig templates.
-    $templates = drupal_find_theme_templates($cache, '.html.twig', drupal_get_path('theme', 'test_theme_twig'));
+    $templates = drupal_find_theme_templates($cache, $extension, drupal_get_path('theme', 'test_theme_twig'));
 
     // Get the template filename and the cache filename for
     // theme_test.template_test.html.twig.
-    $template_filename = $templates['theme_test_template_test']['path'] . '/' . $templates['theme_test_template_test']['template'] . '.html.twig';
+    $template_filename = $templates['theme_test_template_test']['path'] . '/' . $templates['theme_test_template_test']['template'] . $extension;
     $cache_filename = drupal_container()->get('twig')->getCacheFilename($template_filename);
 
     // Navigate to the page and make sure the template gets cached.