Fabio Massimo Ercoli I think you're right. Now that you mention it, it doesn't look that the output of ORM.

But maybe it's the error message of the database?

Kai Hofmann could you tell us more about your setup? Or even better provide a test case based on our test case template: https://github.com/hibernate/hibernate-test-case-templates/tree/master/orm/hibernate-orm-5

Thanks.