diff --git a/stock_reporting_margin.py b/stock_reporting_margin.py
index ff5a8a84c6..d112679675 100644
--- a/stock_reporting_margin.py
+++ b/stock_reporting_margin.py
@@ -20,7 +20,7 @@ class AbstractCommissionMixin:
         cost = super()._column_cost(tables, withs, sign)
         if (Transaction().context.get('include_commission')
                 and 'commission_price' in Move._fields):
-            cost += Sum(
+            cost -= Sum(
                 sign * cls.cost.sql_cast(move.internal_quantity)
                 * Coalesce(move.commission_price, 0))
         return cost
diff --git a/tests/scenario_commission_stock.rst b/tests/scenario_commission_stock.rst
index 4af7a2bc13..8314b1ed7c 100644
--- a/tests/scenario_commission_stock.rst
+++ b/tests/scenario_commission_stock.rst
@@ -191,7 +191,7 @@ Check reporting margin::
     >>> context['include_commission'] = True
     >>> with config.set_context(context=context):
     ...     report, = MarginProduct.find([])
-    >>> report.cost == Decimal('225.0000')
+    >>> report.cost == Decimal('275.0000')
     True
     >>> report.revenue == Decimal('500.0000')
     True