Fax not displaying value in profile edit form

using a profile as user registration with a fax field. when viewing the profile you can see a fax number that exists, but when you click edit the fax field displays as empty.

you can see this on demo here:
view screen it exists: http://drupal.demo.civicrm.org/user/2
edit screen it doesn't exist: http://drupal.demo.civicrm.org/user/2/edit/Name%20and%20Address