diff --git a/modules/stock/product.py b/modules/stock/product.py
index 16f15ae10c..2bf3c86c1e 100644
--- a/modules/stock/product.py
+++ b/modules/stock/product.py
@@ -100,7 +100,7 @@ class Template(metaclass=PoolMeta):
             raise Exception('Bad argument')
         sum_ = 0. if name != 'cost_value' else Decimal(0)
         for product in self.products:
-            sum_ += getattr(product, name)
+            sum_ += getattr(product, name) or 0
         return sum_
 
     @classmethod