diff --git a/core/lib/Drupal/Component/Utility/Html.php b/core/lib/Drupal/Component/Utility/Html.php
index b735fd3..2cfcf8f 100644
--- a/core/lib/Drupal/Component/Utility/Html.php
+++ b/core/lib/Drupal/Component/Utility/Html.php
@@ -90,7 +90,7 @@ public static function cleanCssIdentifier($identifier, array $filter = array(
       $identifier = str_replace('__', '##', $identifier, $double_underscore_replacements);
     }
     $identifier = str_replace(array_keys($filter), array_values($filter), $identifier);
-    if (!isset($filter['__']) && $double_underscore_replacements > 0) {
+    if ($double_underscore_replacements > 0) {
       $identifier = str_replace('##', '__', $identifier);
     }