Embed forms in Symfony

I've added a profile class to sfDoctrineGuard, and in the admin I'm trying to edit the profile part while editing the user, using embed forms as explained here:

http://www.symfony-project.org/blog/2008/11/12/call-the-expert-customizing-sfdoctrineguardplugin

Editing users works, but when I add

"User": [username, password, password_again, Profile]

All I get is an error message :

Widget "Profile" does not exist.

Any help would be appreciated. Is the blog post out of date ?