Marco Belladelli ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=637b480... ) *commented* on HHH-16437 ( https://hibernate.atlassian.net/browse/HHH-16437?atlOrigin=eyJpIjoiYTc4Nj... ) Re: class org.hibernate.mapping.BasicValue cannot be cast to class org.hibernate.mapping.ToOne ( https://hibernate.atlassian.net/browse/HHH-16437?atlOrigin=eyJpIjoiYTc4Nj... ) Hello Marius K ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=70121%3... ) , the error you’re seeing is triggered by a new check we introduced. The mappedBy member of @OneToMany annotation is used to define bi-directional associations between 2 entity types, with the entity which defines it being the non-owning (or inverse) side of the association. You’re using it incorrectly, it doesn’t make sense to indicate a mappedBy pointing to Integer property. Please refer to the User Guide ( https://docs.jboss.org/hibernate/orm/6.2/userguide/html_single/Hibernate_... ) for more information. I think what you’re trying to do might indicating that the id.contractId property of Entity Contractposition should be used as a join column, which case you should use some like @JoinColumn(name="VERTRAG_ID"). ( https://hibernate.atlassian.net/browse/HHH-16437#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16437#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#100221- sha1:78e8bd6 )