Ticket #13709: 13709.patch

post.php

@@ -899 +899 @@
         $args = wp_parse_args($args, $defaults);
         $args = (object) $args;
 
-        $post_type = sanitize_key($post_type);
+        $post_type = substr( sanitize_key($post_type), 0, 20 );
         $args->name = $post_type;
 
         // If not set, default to the setting for public.