[exim] How do you remove specific headers from outgoing emai…

I've got the O'Reilly Exim book (which might be just 3.x specific) but I
was looking to remove specific headers from outgoing email (such as
X-Mailer). I found 'headers_remove' and have the following line in my
Debian unstable exim4's /etc/exim4/exim4.conf.template:

headers_remove = X-Mailer

But when I try to restart Exim, it dies saying:

Starting MTA: 2004-11-06 23:47:16 Exim configuration error in line 407
of /var/lib/exim4/config.autogenerated.tmp:
option "headers_remove" unknown
...

I've tried putting quotes around "X-Mailer" which didn't seem to work,
so can anyone help me and tell me what I'm doing wrong?

Also, I've got my current postfix configuration to strip our the
"Message-Id" header as well so it will get re-written for each outgoing
message. Is this also possible with Exim?

Thanx!

/Hans