diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/BreadcrumbTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/BreadcrumbTest.php
index 914976d..5ee7b6d 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/BreadcrumbTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/BreadcrumbTest.php
@@ -40,6 +40,15 @@ function setUp() {
     $perms = array_keys(module_invoke_all('permission'));
     $this->admin_user = $this->drupalCreateUser($perms);
     $this->drupalLogin($this->admin_user);
+
+    // This test puts menu links in the Tools menu and then tests for their
+    // presence on the page, so we need to ensure that the Tools block will be
+    // displayed in the admin theme.
+    $this->drupalPlaceBlock('system_menu_block:menu-tools', array(
+      'machine_name' => 'system_menu_tools',
+      'region' => 'content',
+      'theme' => \Drupal::config('system.theme')->get('admin'),
+    ));
   }
 
   /**