Regression of @MapsId in hibernate 5.4?

Hi everybody,
I’m trying to upgrade Spring Boot of my project and the latest (development) builds are using Hibernate 5.4 but my project does not work anymore because a class using @MapsId is now unable to populate its id.

The error I get while trying to save a new object is:
Caused by: null id generated for:class

Has anybody noticed the problem?

Is there a workaround, otherwise the problem is blocking my upgrade.

Thanks for any hints