zfs over nfs owner and group

 I have created a new zfs filesystem which I shared via the sharenfs option in
ZFS. On the server where the zfs filesystem resides the permissions (owner and
group) are correct. However, when I nfs mount that zfs filesystem to a client
the owner and group are set to nobody:nobody.

I have tried it on serveral different clients and since we use NIS all clients
know about all owners/groups. Just to be sure I have other directories on the
client with the same owner as the zfs filesystem.

I did compare the parameters of the new zfs filesystem with another zfs
filesystem on another server that works correctly and they appear to be the
same.

Thanks in advance,