Ticket #57420: 57420.diff

src/wp-includes/class-wp-theme-json.php

@@ -481 +481 @@
                         $class_name = static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES[ $element ];
                 }
 
-                return $class_name;
+                return apply_filters( "element_class_name", $class_name, $element );
         }
 
         /**