Don't return unknown field errors if allow_unknown_form_fields is True

djangorestframework/resources.py

@@ -169,6 +169,7 @@ class FormResource(Resource):
             )
 
             # Add any unknown field errors
+            if not self.allow_unknown_form_fields:
                 for key in unknown_fields:
                     field_errors[key] = [u'This field does not exist.']