diff --git a/cost_manage.py b/cost_manage.py
index 9324fe4..ae8ef18 100644
--- a/cost_manage.py
+++ b/cost_manage.py
@@ -1,5 +1,5 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
 
 from trytond.pool import PoolMeta
 
diff --git a/production.py b/production.py
index 9d0f54e..d48f7d3 100644
--- a/production.py
+++ b/production.py
@@ -1,5 +1,6 @@
-#This file is part of Tryton.  The COPYRIGHT file at the top level of
-#this repository contains the full copyright notices and license terms.
+# This file is part of Tryton.  The COPYRIGHT file at the top level of
+# this repository contains the full copyright notices and license terms.
+
 from trytond.model import fields
 from trytond.pool import PoolMeta
 from trytond.modules.cost_manage import ComposeCostSource, CostCenter
@@ -36,5 +37,5 @@ class Production(ComposeCostSource, CostCenter):
         super(Production, cls).done(productions)
         cls.cost_compute(productions)
 
-    def get_factor(self, field=None):
+    def on_change_with_factor(self, field=None):
         return None
\ No newline at end of file