Imapsieve FLAG cause executes a pipe call twice

[DocMAX]

I have this setup:

     imapsieve_mailbox1_name = *
     imapsieve_mailbox1_causes = FLAG
     imapsieve_mailbox1_before = file:~/sieve/learn-flag.sieve

Now if i change the SPAM flag i can see:

Dez 24 14:49:08 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: mailbox 
Junk-E-Mail/dziennik.pl: FLAG event (changed flags: NonJunk)
Dez 24 14:49:08 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: Matched static 
mailbox rule [1]
Dez 24 14:49:08 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: mailbox 
Junk-E-Mail/dziennik.pl: FLAG event (changed flags: Junk)
Dez 24 14:49:08 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: Matched static 
mailbox rule [1]
Dez 24 14:49:11 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: mailbox 
Junk-E-Mail/dziennik.pl: FLAG event (changed flags: Junk)
Dez 24 14:49:11 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: Matched static 
mailbox rule [1]
Dez 24 14:49:11 server dovecot[219886]: 
imap(docmax)<221469><BStCETa3fMzAqAEB>: Debug: imapsieve: mailbox 
Junk-E-Mail/dziennik.pl: FLAG event (changed flags: NonJunk)

And my script is:

require [ "variables" , "imap4flags", "fileinto", "vnd.dovecot.pipe", 
"copy", "imapsieve", "vnd.dovecot.execute" ];

if hasflag :is "Junk" {
     pipe :copy "rspam-spam";
     stop;
}

if hasflag :is "NonJunk" {
     pipe :copy "rspam-ham";
     stop;
}

Dez 24 15:05:24 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam
Dez 24 15:05:24 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-ham
Dez 24 15:05:27 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam
Dez 24 15:05:27 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam
Dez 24 15:05:32 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam
Dez 24 15:05:32 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-ham
Dez 24 15:05:36 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam
Dez 24 15:05:36 server dovecot[222484]: 
imap(docmax)<224089></EW5RDa3UMPAqAEB>: Debug: sieve: action pipe: 
running program: rspam-spam



I espected to have only ONE pipe when i change flag (in Thunderbird). 
Instead i get multiple calls. Why is that and how can i fix it?

Regards,
DocMAX