pWestrich ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *updated* an issue Hibernate ORM ( https://hibernate.atlassian.net/browse/HHH?atlOrigin=eyJpIjoiNWFlM2YzZDU0... ) / Bug ( https://hibernate.atlassian.net/browse/HHH-16664?atlOrigin=eyJpIjoiNWFlM2... ) HHH-16664 ( https://hibernate.atlassian.net/browse/HHH-16664?atlOrigin=eyJpIjoiNWFlM2... ) NPE in MappingMetamodelImpl if inheritence is used in IdClass ( https://hibernate.atlassian.net/browse/HHH-16664?atlOrigin=eyJpIjoiNWFlM2... ) Change By: pWestrich ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) In Hibernate-Core 6.1.7 we could use inheritance in IdClasses like so: {code:java}@Data @NoArgsConstructor @AllArgsConstructor public class ParentPrimaryKey implements Serializable { private UUID parentId; } @Data @NoArgsConstructor @AllArgsConstructor @EqualsAndHashCode(callSuper = true) public class ChildPrimaryKey extends ParentPrimaryKey  { private UUID childId; } {code} But since 6.2.x this will raise a cryptic NPE: {noformat}jakarta.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory; nested exception is java.lang.NullPointerException: Cannot invoke "org.hibernate.metamodel.mapping.EmbeddableValuedModelPart.getNavigableRole()" because "mappingModelPart" is null{noformat} h4. Expected Behavior Instead of an NPE, I would expect a more helpfull message, i.e.: {quote}Illegal embeddable valued model definition: com.example.PK.class. {quote} ( https://hibernate.atlassian.net/browse/HHH-16664#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16664#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:bbd69a1 )