[exim] Strange problem with Exim+SpamAssassin+Kaspersky

Hi list!

I have a really strange problem...
I use Kaspersky and SpamAssassin together with Exim.
Kaspersky check the E-Mails for Virus and Spam, and SpamAssassin just
for Spam.
Now, I'd like to merge the results of both programs, so I'd like to
evaluate the Kaspersky-Header in SpamAssassin, writing a new rule there.

Unfortunately it does not work...
Now, after many many tries, I tried to add this rule to SpamAssassin:

header    TEST                X-AV-scan =~ /yes/
describe  TEST                TEST Kaspersky
score     TEST                0.1

The header will __ALWAYS__ be added by Exim:

acl_check_data:

   warn  message         = X-AV-scan: yes

...

but it does always __NOT__ match...
Now my idea: is it possible, that Exim sends to SpamAssassin a
"version of the message" __WITHOUT__ the added headers?
If yes, how can I change this behavior?

Thanks a lot
Luca Bertoncello
(lucabert@???)