[Dovecot] %d empty string

I am trying to upgrade from dovecot 1.x to Dovecot 2.0.13 on Fedora. My problem is the mail_location setting seems to ignore the %d variable. My my location is as follows:

mail_location = maildir:/var/spool/virtual_mail/%d/%u/Maildir

However, when trying to log in the maillog says it can't find /var/spool/virtual_mail//*myusername*/Maildir/cur. As you can see it just uses an empty string for the %d variable. Can anyone help?

Thanks, Ryan