diff --git a/purchase.py b/purchase.py
index 08d7f65336..66b145c302 100644
--- a/purchase.py
+++ b/purchase.py
@@ -88,8 +88,7 @@ class PurchaseLine:
         res = super(PurchaseLine, cls).read(ids, fields_names=fields_names2)
 
         if not fields_names:
-            fields_names = list(set(cls._fields.keys()
-                    + cls._inherit_fields.keys()))
+            fields_names = cls._fields.keys()
 
         root_ids = []
         for field in fields_names: