strange mtu warnings

Hi again,

This problem only started happening since upgrading from 5.4-p6 to 
6-beta2 on one of my test firewalls.

Aug  9 11:25:46 firewall1 kernel: bridge0: MTU mismatch, frame length 
1514 exceeds 1500 on sis1
Aug  9 11:26:14 firewall1 last message repeated 223 times
Aug  9 11:26:14 firewall1 kernel: bridge0: MTU mismatch, frame length 
1514 exceeds 1500 on sis0
Aug  9 11:26:15 firewall1 kernel: bridge0: MTU mismatch, frame length 
1514 exceeds 1500 on sis1

So on and so forth, for ALL traffic coming in/out. I went from using the 
freebsd bridge to if_bridge which was imported from netbsd for a variety 
of reasons. Bridging same NICs, nothing has changed other than the 
freebsd version, and the switch from the freebsd bridging utility to the 
imported netbsd one. 1514 would be the MTU of ethernet, but not sure why 
it's appearing here.

sis0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 
1500
        options=8<VLAN_MTU>
        inet6 fe80::209:5bff:fee0:af51%sis0 prefixlen 64 scopeid 0x1
        ether 00:09:5b:e0:af:51
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
sis1: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 
1500
        options=8<VLAN_MTU>
        inet6 fe80::209:5bff:fee0:a746%sis1 prefixlen 64 scopeid 0x2
        ether 00:09:5b:e0:a7:46
        media: Ethernet autoselect (10baseT/UTP <full-duplex>)
        status: active
bridge0: flags=41<UP,RUNNING> mtu 1500
        ether ac:de:48:3b:d5:62
        priority 32768 hellotime 2 fwddelay 15 maxage 20
        member: sis1 flags=3<LEARNING,DISCOVER>
        member: sis0 flags=3<LEARNING,DISCOVER>

All three are MTU 1500, so is this a bug or? Any possible solutions?

Thanks,
David