diff --git a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigTransTest.php b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigTransTest.php
index 7f5cfe0..b2687f1 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Theme/TwigTransTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Theme/TwigTransTest.php
@@ -45,8 +45,15 @@ protected function setUp() {
     theme_enable(array('test_theme'));
     \Drupal::config('system.theme')->set('default', 'test_theme')->save();

-    // Enable debug, rebuild the service container, and clear all caches.
+    // Enable twig debug and write to the test settings.php file.
     $this->settingsSet('twig_debug', TRUE);
+    $settings['settings']['twig_debug'] = (object) array(
+      'value' => TRUE,
+      'required' => TRUE,
+    );
+    $this->writeSettings($settings);
+
+    // Rebuild the service container and clear all caches.
     $this->rebuildContainer();
     $this->resetAll();