Mapping of oneToMany with composite key using eclipselink gives me ORA-01400 - oracle

Question

I am trying to map the classic bi-directional oneToMany using eclipselink.
My problem is that when i want to insert a new 'child' i get
SQLIntegrityConstraintViolationException.
The database is described like this :
#Entity
#IdClass(KuponPK.class)
#Table(name = "KUPON", schema = "POST", catalog = "")
public class Kupon implements Serializable {
private Integer id;
private String spil;
private Collection<Kombination> kombinationList;
#OneToMany(mappedBy = "kupon", cascade = CascadeType.PERSIST)
public Collection<Kombination> getKombinationList() {
return kombinationList;
}
public class KuponPK implements Serializable {
private Integer id;
private String spil;
#Id
#Column(name = "ID", nullable = false, insertable = true, updatable = true, precision = 0)
public Integer getId() {
return id;
}
#Id
#Column(name = "SPIL", nullable = false, insertable = true, updatable = true, length = 5)
public String getSpil() {
return spil;
}
#Entity
#Table(name = "KOMBINATION", schema = "POST", catalog = "")
public class Kombination {
private Integer id;
private String sorteringOrden;
private Integer sorteringNr;
private Integer antalSpillede;
private BigDecimal odds;
private Kupon kupon;
#ManyToOne
#JoinColumns({#JoinColumn(name = "KUPON_ID", referencedColumnName = "ID", nullable = false, insertable=false, updatable=false),
#JoinColumn(name = "KUPON_SPIL", referencedColumnName = "SPIL", nullable = false, insertable=false, updatable=false)})
public Kupon getKupon() {
return kupon;
}
In my stateless session i have a Kupon object and i create a new Kombination where i set the Kupon and try to merge, but im getting
Internal Exception: java.sql.SQLIntegrityConstraintViolationException: ORA-01400: cannot insert NULL into ("KOMBINATION"."KUPON_ID")
which is obvious since its part of primary key
I am setting the Kombination to Kupon and the Kupon to Kombination, but that doesnt make any difference
How can can i tell that the key is inside the Kupon object which im setting in the Kombination object ??