The thing is, I cannot recreate it with my tests. As far as I know this should work.

I've created a branch with a test case, adapted from the code you provided. This is the commit with the additional tests: https://github.com/DavideD/hibernate-ogm/commit/1714af00e367ff4f426e5e610d609fbbdc928b65

Maybe you see something that's different compared to your code?