diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
index 722b9ef..f088740 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockTest.php
@@ -194,7 +194,7 @@ function testThemeName() {
       ->set('default', 'seven')
       ->set('admin', 'seven')
       ->save();
-    menu_router_rebuild();
+    \Drupal::service('router.builder')->rebuild();
     $this->drupalGet('admin/appearance');
     $this->drupalGet('admin/structure/block');
     $this->assertText('<"Cat" & 'Mouse'>');