diff --git a/core/modules/ckeditor5/src/HTMLRestrictions.php b/core/modules/ckeditor5/src/HTMLRestrictions.php
index 34a2680f52..d6987cbd91 100644
--- a/core/modules/ckeditor5/src/HTMLRestrictions.php
+++ b/core/modules/ckeditor5/src/HTMLRestrictions.php
@@ -807,16 +807,16 @@ public function toGeneralHtmlSupportConfig(): array {
           if (is_array($value)) {
             $value = array_keys($value);
           }
-          if ($name === 'class') {
-            $to_allow['classes'] = array_keys($value);
-            continue;
-          }
           // Drupal never allows style attributes due to security concerns.
           // @see \Drupal\Component\Utility\Xss
           if ($name === 'style') {
             continue;
           }
           assert($value === TRUE || Inspector::assertAllStrings($value));
+          if ($name === 'class') {
+            $to_allow['classes'] = $value;
+            continue;
+          }
           $to_allow['attributes'][$name] = is_array($value)
             ? ['regexp' => ['pattern' => '/^(' . implode('|', $value) . ')$/']]
             : $value;