XCP-ng 8.3 "Migration compression is not available on this pool"

I cannot enable the Migration Compression on my pool of two 8.3 XCP-ng hosts. The X_O UI says “Migration compression is not available on this pool”. Any ideas what could be the reason and how to make it work?

Are you on the latest patch levels across your pool and latest updates for XO?

yes, restarting XO solved it

did you find it to speed up migrations on 1G?

my tests with Migration Compression on 1Gbps show that it makes no difference at all. Maybe at less than 1Gbps, i.e. across slow WAN uplinks.