It seems correct what you have done. I tested this a while back on a trial/test site, and that is running 5.0.0 now. I know I had this code working, and it doesn’t anymore. Just tested the exact same code on a 4.12.0 site and it works there. Both sites have the same “beta features” settings.
@alex.n - Will somebody from the team check this and see if you guys can replicate it, or has something changed in the API in 5.0.0 ? 