TUN/TAP with IPv6

Does anyone know whether it is possible to use TUN/TAP in TUN mode with
IPv6?

I was trying this with version 1.6 of the TUN/TAP device with a linux
kernel 2.6.12. It showed up that I was able to receive a ICMPv6 echo
request in my test application in TUN mode (using tun0), but my ICMPv6
echo reply does never arrive at the ping6.
Running tcpdump on tun0, I see an error message already regarding the
echo request:

07:17:49.778850 Out ethertype IPv6 (0x86dd), length 120:
0x0000: 6000 0000 0040 3a40 2000 0000 0000 0000
`....@:@........
0x0010: 0000 0000 0000 0002 3000 0000 0000 0000
.........0.......
0x0020: 0000 0000 0000 0003 8000 1c29 006a 0001
............).j..
0x0030: 44ec 011d D...
07:17:49.779960 IP6 , wrong link-layer encapsulationbad-hlen 0

And my echo reply does not show up in the tcpdump output (but in the
ifconfig interface statistics for rx/tx packets it does).

Now, when I switch my test program to use TAP mode with the TUN/TAP
(using device tap0), everything works (I did a manual configuration of
the IPv6 neighbor lists) and no error message is seen in tcpdump.

Maybe this is a configuration problem of the tun0 device?
Thanks for your help!

Michael