diff --git a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
index 399f223..8927433 100644
--- a/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
+++ b/core/tests/Drupal/Tests/Core/Theme/RegistryTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\Tests\Core\Theme;
 
+use Drupal\Core\Extension\Extension;
 use Drupal\Core\Theme\Registry;
 use Drupal\Tests\UnitTestCase;
 
@@ -75,10 +76,7 @@ protected function setUp() {
    */
   public function testGetRegistryForModule() {
     $this->setupTheme('test_theme');
-    $this->registry->setTheme((object) array(
-      'name' => 'test_theme',
-      'filename' => 'core/modules/system/tests/themes/test_theme/test_theme.theme',
-    ));
+    $this->registry->setTheme(new Extension('theme', 'core/modules/system/tests/themes/test_theme/test_theme.info.yml', 'test_theme.theme'));
     $this->registry->setBaseThemes(array());
 
     // Include the module so that hook_theme can be called.
@@ -120,7 +118,7 @@ protected function setupTheme($theme_name = NULL) {
 
 class TestRegistry extends Registry {
 
-  public function setTheme(\stdClass $theme) {
+  public function setTheme(Extension $theme) {
     $this->theme = $theme;
   }