Hi. This is still an issue with H5.0.3. I have bumped the libraries in the updated test case (see hibernate-nullability-H5.zip) nothing else changed. To summarize, when having a bi-directional one-to-many association, Hibernate complains when setting the inverse side (in this example the many side) to not-null. This problem only occurs when putting the relation it in a component. Without the component it works as expected, so this must be a bug.