dovecot - Feb 2008 - Quota Warning problems

Hello, list!

Seems that quota warning feature doesn't work for me.
I have dovecot-1.0.9 with quota-rewrite patch
(http://dovecot.org/patches/1.0/quota-rewrite-1.0.9.diff). Dovecot works as
imap, pop3 server and lda for postfix.

Here is plugin section in dovecot.conf
>>>/etc/dovecot.conf<<<
...
plugin {
  quota = maildir
  quota_rule = *:storage=10M
  quota_warning = storage=50%% /usr/local/bin/quota-warning.sh 50
  quota_warning2 = storage=20%% /usr/local/bin/quota-warning.sh 80
}
>>>cut<<<
>>> /usr/local/bin/quota-warning.sh <<<
#!/bin/sh

echo "Test" > /tmp/script.txt
>>>cut<<<
>>>shell<<<
# /usr/local/dovecot-1.0.9/sbin/dovecot -c
/usr/local/dovecot-1.0.9/etc/dovecot.conf
ILoading modules from directory: /usr/local/dovecot-1.0.9/lib/dovecot/imap
IModule loaded: /usr/local/dovecot-1.0.9/lib/dovecot/imap/lib10_quota_plugin.so
IModule loaded:
/usr/local/dovecot-1.0.9/lib/dovecot/imap/lib11_imap_quota_plugin.so
IEffective uid=65534, gid=65534, homeIQuota root: name= backend=maildir
argsIQuota rule: root= mailbox= bytes=10485760 messages=0
IQuota warning: bytes=5242880 messages=0 command=/usr/local/bin/quota-warning.sh
50
IQuota warning: bytes=2097152 messages=0 command=/usr/local/bin/quota-warning.sh
80
>>>cut<<<

But when user accept 8MB size mail script doesn't execute. There is no
script.txt in /tmp.
Permissions on /usr/local/bin/quota-warning.sh is 755, owner root.
>>>shell<<<
# cat /home/virtual/devel.sitek.net/tolya/Maildir/maildirsize 
10485760S,0C
7983577 1
>>>cut<<<
How can I debug and find out why script doesn't work?

Thank you.

P.S. Sorry for my English.

P.P.S. Quota rules work perfectly.

-- 
Best regards,
   Anatoly Bashmakov