ipfw will not accept a DIVERT rule

[JS (freebsd at stateautomation.com)]

ipfw will not accept a DIVERT rule.  e.g the rule I am trying to add is..
ipfw add 3000 divert 8668 ip from any to any via sis0
The response I get is... ipfw: getsockopt(IP_FW_ADD): Invalid argument
I have built a custom kernel with the following optional lines
options IPFIREWALL
options IPFIREWALL_VERBOSE
options IPFIREWALL_VERBOSE_LIMIT
options IPDIVERT
Does anyone know why the system will not accept the divert rule? Thanks.

J.S.