for field in seminar._meta.many_to_many:
 
-                        if field.remote_field.to == Document:
+                        if field.remote_field.model == Document:
                             source = getattr(seminar, field.attname)
                             destination = getattr(clone, field.attname)
                             for item in source.all():
                                 destination.add(item_clone)
                                 # print ("media cloned and assigned:", item_clone)
 
-                        elif field.remote_field.to == Media:
+                        elif field.remote_field.model == Media:
                             source = getattr(seminar, field.attname)
                             destination = getattr(clone, field.attname)
                             for item in source.all():