smtpd.conf and junk

[Thuban]

Hi,
I can't figure how to make this "junk" argument to work as 
mentioned in The smtpd.conf manpages :

        If the junk argument is provided, the message will be
        moved to the Junk folder if it contains a positive X-Spam
        header.


spams detected by spamassassin have multiple X-Spam-* headers, but aren't placed
into Junk folder.

Any advice ?



-- 
    thuban