diff --git a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
index ac7b6b7..f8068f2 100644
--- a/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
+++ b/core/modules/system/lib/Drupal/system/Controller/ThemeController.php
@@ -144,9 +144,6 @@ public function enable(Request $request) {
    *   the token is invalid.
    */
   public function defaultTheme(Request $request) {
-    // Set the page title.
-    drupal_set_title($this->t('Set default theme'));
-
     $theme = $request->query->get('theme');
     $token = $request->query->get('token');
     if (isset($theme) && isset($token) && drupal_valid_token($token, 'system-theme-operation-link')) {
diff --git a/core/modules/system/system.routing.yml b/core/modules/system/system.routing.yml
index 274f51f..d07cd2b 100644
--- a/core/modules/system/system.routing.yml
+++ b/core/modules/system/system.routing.yml
@@ -225,6 +225,7 @@ system_theme_default:
   pattern: '/admin/appearance/default'
   defaults:
     _controller: 'Drupal\system\Controller\ThemeController::defaultTheme'
+    _title: 'Set default theme'
   requirements:
     _permission: 'administer themes'