Ticket #39077: 39077.1.diff

src/wp-includes/post.php

@@ -115 +115 @@
                 ),
                 'public' => false,
                 '_builtin' => true, /* internal use only. don't use this when registering your own post type. */
-                'hierarchical' => false,
+                'hierarchical' => true,
                 'rewrite' => false,
                 'delete_with_user' => false,
                 'query_var' => false,