Mailbox doesn't allow inferior mailboxes

["Roger Berger" <roger at berger dot nl>]

Hi,

When imapsync tries to add maps in an already existing map I get this error:
Mailbox doesn't allow inferior mailboxes

Does anybody know how to "repair" this?
I am running imapsync 2.86 with 3.19 and dovecot with sendmail.

Thanks,

Roger