dovecot - Mar 2012 - importing plain mboxes to dovecot maildirs

Is there way to import old plain mboxes via dsync? It complains about 
lack of index files:

ponto:(admin)~>dsync mirror mbox:~/mail
dsync(admin): Error: Failed to sync mailbox sent-mail: Mailbox GUIDs are 
not permanent without index files
dsync(admin): Error: Failed to sync mailbox saved-messages: Mailbox 
GUIDs are not permanent without index files
dsync(admin): Error: Failed to sync mailbox sent-mail-feb-2012: Mailbox 
GUIDs are not permanent without index files

On 17.3.2012, at 8.36, Radim Kolar wrote:
> Is there way to import old plain mboxes via dsync? It complains about lack
of index files:
> 
> ponto:(admin)~>dsync mirror mbox:~/mail
> dsync(admin): Error: Failed to sync mailbox sent-mail: Mailbox GUIDs are
not permanent without index files
> dsync(admin): Error: Failed to sync mailbox saved-messages: Mailbox GUIDs
are not permanent without index files
> dsync(admin): Error: Failed to sync mailbox sent-mail-feb-2012: Mailbox
GUIDs are not permanent without index files
Well, you can work around if by letting it create indexes. Hm. Why exactly
can't it create indexes? Do you have some setting disabling them?