correction, I hadn't updated my server in a while, stretch itself is on 0.6.5.9 also, but stretch-backports is on 0.7.6 (not sure when that happened exactly)
[2018-03-09] Accepted zfs-linux 0.7.6-1~bpo9+1 (source amd64 all) into stretch-backports (Aron Xu)