The fix for HHH-12436 involves correcting the foreign key direction for some one-to-one assocations. In the process of making changes I see that we have a unit test that has a unidirectional one-to-one association mapped with constrained="false". [1] ModelBinder assumes that <one-to-one ... constrained = "true"> means that the foreign key direction is FROM_PARENT; if constrained = "false", it assumes that the foreign key direction is TO_PARENT. [2] It seems odd to me that the foreign key direction for a unidirectional association would be TO_PARENT. Should the unit test have constrained = "true"? If not, should ModelBinder check to see if the association is bidirectional and determine which side owns the association? This would probably require adding a SecondPass. Please let me know your thoughts. Regards, Gail [1] https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src... [2] https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src...