[Dovecot] dovecot trying to update my sieve directory

[Mathieu R.]

Hello,

i got an error in maillog, dovecot trying tu update my sieve directory 
:

2012-11-23T11:01:33.943047+00:00 localhost dovecot: 
imap(math...@400iso.net): Error: 
stat(/srv/vmail/400iso.net/math...@400iso.net/.dovecot.sieve/tmp) 
failed: Not a directory

this cause no problem but i probably misconfigured something...
here is my dovecot.conf :


protocols = imap pop3 sieve

mail_home = /srv/vmail/%d/%u
mail_location = maildir:~
mail_plugins = $mail_plugins quota

ssl_cert = </etc/ssl/private/server.crt
ssl_key = </etc/ssl/private/server.key

service auth {
  unix_listener auth-client {
    group = postfix
    mode = 0660
    user = postfix
  }
  user = root
}

passdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}

userdb {
  args = /etc/dovecot/dovecot-sql.conf
  driver = sql
}

protocol lda {
      mail_plugins = $mail_plugins sieve
      postmaster_address = postmas...@400iso.net
      hostname = 400iso.net
}

managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope 
encoded-character vacation subaddress comparator-i;ascii-numeric 
relational regex imap4flags copy include variables body enotify 
environment mailbox date ihave

plugin {
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
#  sieve_global_dir = /srv/vmail/sieve/
  quota = fs:vm quota
  quota_rule = *:storage=5G
}


protocol imap {
        mail_plugins = $mail_plugins imap_quota
}

--
Mathieu Rousseau
http://400iso.net/