[exim] unknown ACL condition/modifier in "deny spam = nobody…

Hi.

I am running exim-4.50 on debian 3.2 sarge.  I have spamassassin running.
When I try to enable a simple acl to use it as the docs show,
  acl_check_data:
      deny spam = nobody
           message = SPAM mail rejected

I get the following error when restarting exim,

    Exim configuration error in line 425 of /etc/exim4/exim4.conf:
      error in ACL: unknown ACL condition/modifier in "deny spam = nobody"

Is this an indicator that spam assassin support is not compiled into the
Debian exim package? Or am I overlooking something else?

I hope I am not overlooking a FAQ. I have been searching the FAQs and
google. I have found references to similar errors, but not related to
the "deny spam" setting to enable spamassassin.