diff --git a/core/modules/system/src/Tests/Theme/TwigEnvironmentTest.php b/core/modules/system/src/Tests/Theme/TwigEnvironmentTest.php
index 235db35..ecf38b1 100644
--- a/core/modules/system/src/Tests/Theme/TwigEnvironmentTest.php
+++ b/core/modules/system/src/Tests/Theme/TwigEnvironmentTest.php
@@ -83,5 +83,34 @@ public function testTemplateNotFoundException() {
     }
   }
 
+  /**
+   * Ensures that cacheFilename() varies by extensions + deployment identifier.
+   */
+  public function testCacheFilename() {
+    /** @var \Drupal\Core\Template\TwigEnvironment $environment */
+    // Note: Later we refetch the twig service in order to bypass its internal
+    // static cache.
+    $environment = \Drupal::service('twig');
+
+    $original_filename = $environment->getCacheFilename('core/modules/system/templates/container.html.twig');
+    \Drupal::getContainer()->set('twig', NULL);
+
+    \Drupal::service('module_installer')->install(['twig_extension_test']);
+    $environment = \Drupal::service('twig');
+    $new_extension_filename = $environment->getCacheFilename('core/modules/system/templates/container.html.twig');
+    \Drupal::getContainer()->set('twig', NULL);
+
+    // Change the deployment identifier.
+    $settings = Settings::getAll();
+    $settings['deployment_identifier'] = '7297';
+    new Settings($settings);
+
+    $environment = \Drupal::service('twig');
+    $deyploment_identifier_change_filename = $environment->getCacheFilename('core/modules/system/templates/container.html.twig');
+
+    $this->assertNotEqual($new_extension_filename, $original_filename);
+    $this->assertNotEqual($deyploment_identifier_change_filename, $original_filename);
+  }
+
 }