[Dovecot] is it posible to autocreate imap folders with non ascii chars?

[Igor Zinovik]

	Hello.

I'm migrating from cyrus to dovecot and now after i converted mailboxes to
Maildir.  Some users already has imap folders with cyrillic chars.
How could i autocreate folders with cyrillic chars?  When i type
something like:
...
autocreate = utf8_chars
autosubscribe = utf8_chars
...

In logs i see that dovecot complains:
Apr 05 16:21:43 imap(pavelkor): Debug: autocreate: Failed to create mailbox utf8_chars: Invalid mailbox name

It is even possible to achieve?