Marco Belladelli ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=637b480... ) *commented* on HHH-16671 ( https://hibernate.atlassian.net/browse/HHH-16671?atlOrigin=eyJpIjoiOTFiMz... ) Re: Unable to query key attribute that uses AttributeConverter ( https://hibernate.atlassian.net/browse/HHH-16671?atlOrigin=eyJpIjoiOTFiMz... ) Hello Piotr Przybylski ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) , as you can read from the @Convert annotation’s javadoc ( https://jakarta.ee/specifications/persistence/3.1/apidocs/jakarta.persist... ) , JPA explicitly specifies that you should not apply converters to ID attributes. In fact, both Hibernate 5 and 6 ignore any conversion information applied to identifiers. The error you’re getting is due to the stricter SQL function argument type validation that was introduced with Hibernate 6 and to the fact that YearMonth doesn’t map to a comparable SQL type. ( https://hibernate.atlassian.net/browse/HHH-16671#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16671#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#100225- sha1:85acc52 )