Jan-Willem Gmelig Meyling ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *commented* on HHH-13866 ( https://hibernate.atlassian.net/browse/HHH-13866?atlOrigin=eyJpIjoiZDA5ZW... ) Re: OneToOne-association produces error on 5.4.0+ when using PostgreSQL ( https://hibernate.atlassian.net/browse/HHH-13866?atlOrigin=eyJpIjoiZDA5ZW... ) Your mapping is IMO still invalid, it might have worked before due to a flaw. The one to one implementation of 5.3 was definitely flawed. We solved a couple of bugs. One of which where the parent side of the one to one association was actually treated as child. I wouldn’t classify this issue as a bug personally until we have shown that the issue persists after fixing the mapping. That means that the identifier of your child side of the association should be persistable/insertable. Please consider writing a test case based on the Hibernate test case template so we can play around with the model and see what needs to be fixed. ( https://hibernate.atlassian.net/browse/HHH-13866#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-13866#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100126- sha1:9bc00fe )