diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
index d4d7451..52eeb92 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
@@ -509,6 +509,7 @@ function testMenuLinkOptions() {
       'options' => array(
         'attributes' => array(
           'title' => 'Test title attribute',
+          'data_test' => '',
         ),
         'query' => array(
           'testparam' => 'testvalue',
@@ -520,6 +521,7 @@ function testMenuLinkOptions() {
     // Load front page.
     $this->drupalGet('test-page');
     $this->assertRaw('title="Test title attribute"', 'Title attribute of a menu link renders.');
+    $this->assertRaw('data_test = ""', 'check_plain() does not double-escape entities in strings.');
     $this->assertRaw('testparam=testvalue', 'Query parameter added to menu link.');
   }