Mark match an Tarpit failure

The following work for me:

iptables -A INPUT -m mark --mark 13 -j DROP
iptables -A INPUT -p tcp -j TARPIT

but the following does not and returns "Invalid
Argument":

iptables -A INPUT -m mark --mark 13 -j TARPIT

what am I missing?

..don

[email protected]
White Plains, NY