ZFS on Debian GNU/kFreeBSD

[Tuco]

Hello

I've been doing some experiments with ZFS on Debian GNU/kFreeBSD. My
goal is to setup ZFS as root filesystem. I setup the ZFS tools in
Debian with some tricks (my blog has detail about them:
http://tucobsd.blogspot.com/2010/07/how-to-enable-zfs-on-debian-gnukfreebsd.html),
but when trying to install GRUB in a ZFS filesystem I run into
trouble:

/usr/sbin/grub-probe: error: cannot find a device for /boot/grub (is
/dev mounted?).

I checked the command run by grub-install; in a normal (UFS) system
this command prints /dev/ad0s2.

Is this a known problem? Should I investigate? Can you give some guideline?