diff --git a/core/modules/system/src/Tests/Theme/ThemeTest.php b/core/modules/system/src/Tests/Theme/ThemeTest.php
index e7e49c3..ee26c4d 100644
--- a/core/modules/system/src/Tests/Theme/ThemeTest.php
+++ b/core/modules/system/src/Tests/Theme/ThemeTest.php
@@ -287,8 +287,7 @@ function testRegionClass() {
     // Place a block.
     $this->drupalPlaceBlock('system_main_block');
     $this->drupalGet('');
-    $elements = $this->cssSelect("div.new_class");
-    debug($elements);
+    $elements = $this->cssSelect(".region-sidebar-first.new_class");
     $this->assertEqual(count($elements), 1, 'New class found.');
   }
 }