java.lang.ClassCastException: class org.hibernate.mapping.BasicValue cannot be cast to class org.hibernate.mapping.ToOne (org.hibernate.mapping.BasicValue and org.hibernate.mapping.ToOne are in unnamed module of loader 'app')

@Entity
public class Contract implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    private Integer contractId;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "id.contractId")
    @OrderBy(value = "id.positionNumber")
    private List<Contractposition> contractpositions = new ArrayList<>();

@Entity
public class Contractposition implements Serializable {

    private static final long serialVersionUID = 1L;

    @EmbeddedId
    @AttributeOverrides(
            {
                    @AttributeOverride(name = "contractId", column = @Column(name = "VERTRAG_ID", nullable = false)),
                    @AttributeOverride(name = "positionNumber", column = @Column(name = "POSITIONSNUMMER", nullable = false))})
    private ContractpositionId id;

@Embeddable
public class ContractpositionId implements Serializable {

	private static final long serialVersionUID = 1L;

	@Column(name = "VERTRAG_ID", nullable = false)
	private Integer contractId;

	@Column(name = "POSITIONSNUMMER", nullable = false)
	private int positionNumber;