[Dovecot] invalid mailbox name

Hi,

while migrating all mail from our old to our new server (using offlineimap, imap -> imap), I get the following error for one of my user's mailboxes:

ERROR: Folder 'Organisations.RS Env & IJRS'[local_hoekman] could not be created. Server responded: ('NO', ['Invalid mailbox name: Organisations.RS Env & IJRS'])

I suppose this is because of the ampersand in the mailbox name? Because other folder with spaces in it go just fine...

Is this a fixed thing? Why was my user able to create the folder once? And why is dovecot 1.2.15 refusing to create the folder now?

Migration is from dovecot 1.1.11 to 1.2.15.

Thanks, Vincent.