JPA 2 Chave composta e relacionamento

@Embeddable
public class PortBrasPK implements Serializable {
    
    @ManyToOne
    @JoinColumn(name="BRAS_FK")
    private Bras bras;
    
    @Column(name = "PORT_BRAS", length = 20, nullable = false)
    private String port;

@Entity
@Table(name = "PORT_BRAS")
public class PortBras implements Serializable {

    @EmbeddedId()
    private PortBrasPK portBrasPK;
    @Column(name = "TOTAL_CUSTOMER", nullable = false)
    private int totalCustomer;
    @Column(name = "ACTIVE_CUSTOMER")
    private int activeCustomer;

@Entity
@Table(name = "DSLAM")
public class Dslam implements Serializable {
    
    @Id
    @Column(name="IP_DSLAM")
    private String ipDslam;    
    @ManyToOne
    @JoinColumns({
        @JoinColumn(name="BRAS_FK", referencedColumnName="bras"),
        @JoinColumn(name="PORT_BRAS", referencedColumnName="port")
    })
    private PortBras portBras;    
    @Column(name = "NAME", nullable = false, length = 255)
    private String name;
    @Column(name = "TYPE", nullable = false, length = 100)
    private String type;
    @Column(name = "TOTAL_CUSTOMER", nullable = false)
    private int totalCustomer;
    @Column(name = "ACTIVE_CUSTOMER", nullable = false)
    private int activeCustomer;

Exception Description: The @JoinColumns on the annotated element [private br.com.gvt.acct.entity.PortBras br.com.gvt.acct.entity.Dslam.portBras] from the entity class [class br.com.gvt.acct.entity.Dslam] is incomplete. When the source entity class uses a composite primary key, a @JoinColumn must be specified for each join column using the @JoinColumns. Both the name and the referenceColumnName elements must be specified in each such @JoinColumn.