diff --git a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
index 20550f5..4f2847a 100644
--- a/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Extension/ThemeHandlerTest.php
@@ -271,6 +271,7 @@ public function testRebuildThemeData() {
         'style.css' => DRUPAL_ROOT . '/core/themes/seven/style.css',
         'css/components/buttons.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/buttons.css',
         'css/components/buttons.theme.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/buttons.theme.css',
+        'css/components/dropbuttons.css' => DRUPAL_ROOT . '/core/themes/seven/css/components/dropbuttons.css',
       ),
     ), $info->info['stylesheets']);
     $this->assertEquals(DRUPAL_ROOT . '/core/themes/seven/screenshot.png', $info->info['screenshot']);