mport trouble

I seem to be having a little trouble with the iptables mport match in
a basic sarge installation (3.0r0a-ppc).

$ iptables -A FORWARD -p tcp -j ACCEPT
$

Ok, no problem so far.

$ iptables -A FORWARD -p tcp -m mport -j ACCEPT
iptables v1.2.11: mport expects an option
Try `iptables -h' or 'iptables --help' for more information.
$

Ok, that makes perfect sense. We haven't told it which port, but at
least our installation supports mport.

$ iptables -A FORWARD -p tcp -m mport --dports 22 -j ACCEPT
iptables: No chain/target/match by that name
$

Now this is weird. The same command works fine in other places
(meaning it's probably not a syntax error). Any ideas what I'm doing
wrong?