diff --git a/addons/stock/models/stock_move_line.py b/addons/stock/models/stock_move_line.py
index bb93b1c224b..f914f8aa00f 100644
--- a/addons/stock/models/stock_move_line.py
+++ b/addons/stock/models/stock_move_line.py
@@ -141,7 +141,7 @@ class StockMoveLine(models.Model):
         help him. This onchange will warn him if he set `qty_done` to a non-supported value.
         """
         res = {}
-        if self.product_id.tracking == 'serial':
+        if self.qty_done and self.product_id.tracking == 'serial':
             if float_compare(self.qty_done, 1.0, precision_rounding=self.move_id.product_id.uom_id.rounding) != 0:
                 message = _('You can only process 1.0 %s for products with unique serial number.') % self.product_id.uom_id.name
                 res['warning'] = {'title': _('Warning'), 'message': message}