[exim] spam acl condition: Broken pipe on spamd socket

Hi all,
I have set up exim4-daemon-heavy on Debian together with spamassassin.
I wanted to use the ACL variant to call spamassassion. I uncommented
the section in the data acl, enabled spamassassin in it's
configuration file, tested spamassassin (by spamassassin -t <
spamtest.txt), it all worked. However, emails I send dont get
classified with X-Spam-Headers. I get an error in my exim paniclog:
"spam acl condition: Broken pipe on spamd socket".

Any ideas, what I can do, try out?

Thanks,
Joerg