tcpdump not capturing NAT packets

Hi,

I've got OpenVPN set up on my linode to masquerade traffic in the usual fashion:

iptables –table nat --append POSTROUTING --source 192.168.24.0/24 --out-interface eth0 --jump MASQUERADE

It works fine except I cannot capture any of the packets being sent over eth0:

tcpdump -i eth0 -w traffic.eth0

It captures other tcp traffic but I cannot find any of the connections being listed by netstat-nat:

$ netstat-nat

Proto NATed Address Destination Address State

tcp 192.168.24.7:50748 38.229.70.20:irc ESTABLISHED

Any idea what's wrong?