I've tried everything I can to write a test for this that fails. It keeps passing. This is with 5.2 while you mention 5.1. Have you tried with 5.2 to see if this is something that was fixed in between? That or take a look at the test I wrote to see if you can spot the difference or other wise make it fail.

Its https://github.com/hibernate/hibernate-orm/commit/e9263758fe8c5466f27c632d409595aa973b39d3 if you can't see the Jira link to the commit