This looks very much like HHH-8999 Closed , which was fixed in 5.0.10, 5.2.1, 5.1.1.

Are you setting hibernate.order_updates=true or hibernate.order_inserts=true? If so, TaskId would need to implement Comparable.

Please let us know. If you are still having problems, please attach a short but complete test case that reproduces the reported bug.