[Dovecot] Syncing shared mailboxes

Hi, while trying to sync the mailboxes of several users who use and share their mailboxes dsync prints this message:

dsync-local(<user-who-uses-shared-mailbox>): Warning: Subscriptions file /home/<user-who-uses-shared-mailbox>/Maildir/subscriptions: Removing invalid entry: shared/<sharing-user>/<shared-folder>

The problem is: Every user has to subscribe the shared folder again after each run of dsync... Is dsync capable of syncing shared mailboxes? Are there any preliminaries to do so?

thanks in advance, Knud