[Dovecot] Unexpected input from auth master: CUID

Hello, I'm using postfix(2.4.5) and dovecot(1.0.5), and till now I have been using postfix deliver agent. Now I have tried to reconfigure postfix to use the dovecot LDA, but I'm getting some strange error: Sep 9 18:07:57 hostname deliver(username@domain.tld): BUG: Unexpected input from auth master: CUID^I5

For IMAP and POP3 my configuration works fine. I have tried it also with dovecot versions 1.0.4 and 1.0.1, but the behaviour is the same. What can be the reason of this? What should I look for to get more details what can causing this?

I have this line in postfix master file:

dovecot unix - n n - - pipe flags=DRhu user=mails:mails argv=/opt/dovecot-1.0.5-1/libexec/dovecot/deliver -f ${sender} -d ${recipient}

In main.cf: dovecot_destination_recipient_limit = 1 virtual_transport = dovecot

Relevant parts of dovecot.conf:

auth default { passdb sql { args = /path/to/dovecot-sql.conf } userdb sql { args = /path/to/dovecot-sql.conf }

socket listen {
    client {
      path = /var/run/dovecot/auth-master
      mode = 0600
      user = mails
      group = mails
    }
}

}

protocol lda { postmaster_address = postmaster@domain.tld auth_socket_path = /var/run/dovecot/auth-master }

And relevant parts of dovecot-sql.conf:

driver = mysql

password_query = SELECT address as user, passwd as password FROM mail_users WHERE address='%u' user_query = SELECT CONCAT('/home/',maildir) as home, 999 as uid, 999 as gid FROM mail_users WHERE address='%u'

Thanks, BB