dsync: INBOX Can't be deleted

Hi,

I am Migrating an old cyrus mailserver to dovecot.

in the old cyrus Mailserver all User Mailboxes are sub-mailboxes of their INBOX.

I have to preserve that structure.

During Migration with dsync I get these Errors:

Error: Mailbox INBOX sync: mailbox_delete failed: INBOX can't be deleted

Is there a way to work around these Errors ?

Thanks Christoph