diff --git a/peewee.py b/peewee.py
index <HASH>..<HASH> 100644
--- a/peewee.py
+++ b/peewee.py
@@ -5116,9 +5116,9 @@ class Model(with_metaclass(ModelBase, Node)):
         return new_data
 
     def _populate_unsaved_relations(self, field_dict):
-        for foreign_key in self._meta.refs:
+        for foreign_key_field in self._meta.refs:
+            foreign_key = foreign_key_field.name
             conditions = (
-                foreign_key in self._dirty and
                 foreign_key in field_dict and
                 field_dict[foreign_key] is None and
                 self.__rel__.get(foreign_key) is not None)
Fixed unsaved relation population

Fixes #<I>



1) The keys in the respective dicts is the foreign key's name, not the field itself.

2) According to `ForeignKeyAccessor.__set__`, foreign key fields are never dirty.