SA not rewriting subject

[Tom]

I am running Spamassassin 3.1.7 on a Fedora core 6 box
Everything appears to be working but the subject is not getting 
rewritten to show that the spam is spam
my /etc/mail/spamassassin/local.cf  has the following line in it.
rewrite_header subject ****SPAM(_SCORE_)****

Am I missing something?