diff --git a/stock.py b/stock.py
index 6cd0fca4cb..f8510717bc 100644
--- a/stock.py
+++ b/stock.py
@@ -151,9 +151,8 @@ class Move(metaclass=PoolMeta):
 class ShipmentIn(metaclass=PoolMeta):
     __name__ = 'stock.shipment.in'
 
-    @classmethod
-    def _get_inventory_moves(cls, incoming_move):
-        move = super(ShipmentIn, cls)._get_inventory_moves(incoming_move)
+    def _get_inventory_move(self, incoming_move):
+        move = super()._get_inventory_move(incoming_move)
         if move and incoming_move.lot:
             move.lot = incoming_move.lot
         return move
@@ -205,10 +204,8 @@ class ShipmentOut(metaclass=PoolMeta):
 class ShipmentOutReturn(metaclass=PoolMeta):
     __name__ = 'stock.shipment.out.return'
 
-    @classmethod
-    def _get_inventory_moves(cls, incoming_move):
-        move = super(ShipmentOutReturn,
-            cls)._get_inventory_moves(incoming_move)
+    def _get_inventory_move(self, incoming_move):
+        move = super()._get_inventory_move(incoming_move)
         if move and incoming_move.lot:
             move.lot = incoming_move.lot
         return move