NFSv4 - ACLs not working

I've setup an NFSv4 server (Debian) and client (Ubuntu/Mythbuntu). It seems that uid username mapping is working nicely out-of-the-box (I get correct usernames on ls -l if the usernames match between the two boxes, even if the uids don't), but ACLs are not working. I've installed nfs4-acl-tools and I can read the ACLs correctly on the client, but they don't get applied.

What needs to be done for ACLs to work?

To clarify; username mapping works for regular permissions. ACLs are applied using uid/gid (I can even set ACLs by uid and they work).

you need nfs4 acls, not posix acls. As far as I know, no linux nfs server provides that yet.

The easies way to get it is to get a zfs enabled system, like nexentastor. If you have a Netapp filer that one works great too.