mapall ignored in 15.0 exports

Hi
I upgraded my 14.4 server to 15.0 this week and I now have permissions issue on one NFS share.
It looks like mapall option is ignored.
I have not changed anything in /etc/exports or any other setting that seems to be related to NFS.

This is the exports line for that share:
/mnt/ssdpool/shares/downloads -alldirs -mapall=spons:spons	-network=192.168.178.0/24

Any ideas ?

Cheers,
  Paul