Ticket #13794: to_field_formsets.2.patch

django/forms/models.py

@@ -859 +859 @@
             form.data[form.add_prefix(self.fk.name)] = None
 
         # Set the fk value here so that the form can do its validation.
-        setattr(form.instance, self.fk.get_attname(), self.instance.pk)
+        fk_value = self.instance.pk
+        if self.fk.rel.field_name != self.fk.rel.to._meta.pk.name:
+            fk_value = getattr(self.instance, self.fk.rel.field_name)
+            fk_value = getattr(fk_value, 'pk', fk_value)
+        setattr(form.instance, self.fk.get_attname(), fk_value)
         return form