diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index 223d234..ee5fdb8 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -8,6 +8,7 @@
 use Drupal\Component\Utility\Xss;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Template\Attribute;
 
 /**
  * Implements hook_preprocess_HOOK() for HTML document templates.
@@ -89,11 +90,8 @@ function seven_preprocess_block(&$variables) {
   if (isset($variables['title_suffix']['contextual_links'])) {
     unset($variables['title_suffix']['contextual_links']);
     unset($variables['elements']['#contextual_links']);
-    foreach ($variables['attributes']['class'] as $key => $class) {
-      if ($class === 'contextual-region') {
-        unset($variables['attributes']['class'][$key]);
-      }
-    }
+    $attribute = new Attribute(array('class' => $variables['attributes']['class']));
+    $attribute->removeClass('contextual-region');
   }
 }