Eclipse error on mapping with @EmbeddedId

I have an entity with composite key so I use the @Embeddable and @EmbeddedId annotations. Embeddable class looks like this :

@Embeddable
public class DitaAdminAccountSkillPK implements Serializable {

  @ManyToOne
  @JoinColumn(name = "admin_id")
  private DitaAdmin admin;

  @ManyToOne
  @JoinColumn(name = "account_id")
  private DitaAccount account;

  //constructor, getters, setters...
}

And the entity that uses it :

@Entity
public class DitaAdminAccountSkill {

  @EmbeddedId
  private DitaAdminAccountSkillPK id;

  //constructor, getters, setters...
}

Now I want to map the entity in another entity like this :

@OneToMany(fetch = FetchType.LAZY, mappedBy = "id.admin")
private List<DitaAdminAccountSkill> accountSkills;

Notice the mappedBy = "id.admin" which refers to admin field in DitaAdminAccountSkillPK using the id field of DitaAdminAccountSkill.

This compiles and runs just fine. However, in eclipse there is an error displayed that says : In attribute 'accountSkills', the "mapped by" value 'id.admin' cannot be resolved to an attribute on the target entity.

Note that this is a JPA Problem meaning the JPA facet is complaining. Now, I know I could use @IdClass instead but I am just wondering why does it think its an error. Or maybe I do something terribly wrong ?