Fatal errors in Wiki plugin 404 page

When the 404 page template gets loaded for the Wiki plugin a fatal error is served. It appears there's a call to a method in the Wiki class that doesn't exist?

Here's the error - Fatal error: Call to undefined method Wiki::get_new_wiki_form() in /srv/www/wordpress-trunk/wp-content/plugins/wiki/404-incsub_wiki.php on line 17