dovecot - May 2006 - statfs() error message

i use openbsd/i386, dovecot-1.0b7

i see the error message in maillog
dovecot: statfs(mail/username) failed: No such file or directory

i guess the statfs() can not find the directory,
because i run dovecot-imap in chroot

userdb static {
args = uid=34567 gid=34567 home=/var/./mail
}

i am sure, i have this directory "/var/mail/username",
and i add "nfs_check = no" to dovecot.conf, the error message will
gone