diff --git a/odooly.py b/odooly.py
index e3e345e..7fc8b6a 100644
--- a/odooly.py
+++ b/odooly.py
@@ -1415,7 +1415,7 @@ def __repr__(self):
                                  self._name, ids)
 
     def __dir__(self):
-        attrs = set(self.__dict__) + set(self._model._keys)
+        attrs = set(self.__dict__) | set(self._model._keys)
         return sorted(attrs)
 
     def __bool__(self):