The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations?

Question

System.InvalidOperationException: 'Unable to determine the principal end of an association between the types 'EF_CODEFIRST_Filmler.Director' and 'EF_CODEFIRST_Filmler.Film'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.'

    public class Film
    {
     [Key]
     public int FilmID { get; set; }
     public string Title { get; set; }

     public virtual Director Director { get; set; }
     public virtual Language Language { get; set; }
     public virtual ICollection<Actor> Actors { get; set; }
    }

    public class Director
    {
     [Key]
     public int FilmID { get; set; }
     public string DirectorName { get; set; }
     public Nullable<int> DirectorLanguageID { get; set; }

   
     public virtual Language Language { get; set; }
     public virtual Film Film { get; set; }
    }