[Dovecot] fts squat non-english search for 2 words

[vuser1 at test123.ru]

Hello,

It looks I encoutered a bug or misconfiguration. fts_squat search for subject and body works excellent for English mails. For non-English (in particular, Russian) it works only when query consists of 1 word. Phrases - 2 and more words - always returns nothing. Example: search for "planet" ("планета") returns results, search for "Earth" ("Земля") also returns results, but "planet Earth" ("планета Земля") returns nothing. But there are emails having exact phrase "planet Earth". This problem occurs only for non-English queries, both for search in subject and in email body.
I tried web-mail Horde 3.2 and Thunderbird.
I turned fts plugin off and it correctly finds phrases with 2 and more russian words! So problem is squat. Is it a bug or known config issue?

OS: Debian 5.0, installed as openVZ container inside Ubuntu 8.04. 
Dovecot: 1.2.4, from backports.org
Ext3 filesys

dovecot -n
--------------
# 1.2.4: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.24-24-openvz i686 Debian 5.0.3 simfs
log_timestamp: %Y-%m-%d %H:%M:%S 
protocols: imap imaps pop3 pop3s
ssl_cert_file: /etc/ssl/test123/test123.full.crt
ssl_key_file: /etc/ssl/test123/priv/test123.key
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
last_valid_uid: 500
mail_privileged_group: mail
mail_location: maildir:/var/mail/%u
mbox_write_locks: fcntl dotlock
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_plugins(default): quota imap_quota fts fts_squat
mail_plugins(imap): quota imap_quota fts fts_squat
mail_plugins(pop3): 
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
imap_client_workarounds(default): outlook-idle delay-newmail
imap_client_workarounds(imap): outlook-idle delay-newmail
imap_client_workarounds(pop3): 
pop3_client_workarounds(default): 
pop3_client_workarounds(imap): 
pop3_client_workarounds(pop3): outlook-no-nuls oe-ns-eoh
lda:
  postmaster_address: postmaster at test123.ru
  hostname: test123.ru
  sendmail_path: /usr/sbin/sendmail
  auth_socket_path: /var/run/dovecot/auth-master
  mail_plugins: quota sieve
  log_path: 
  info_log_path: 
auth default:
  mechanisms: plain login
  user: nobody
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: passwd
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: prefetch
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: mail
    master:
      path: /var/run/dovecot/auth-master
      mode: 432
      user: vmail
      group: mail
plugin:
  acl: vfile:/etc/dovecot/acls
  trash: /etc/dovecot/trash.conf
  fts: squat
  fts_squat: partial=4 full=20
---------------
(with full=10 problem persists)