diff --git a/openerp/fields.py b/openerp/fields.py
index d4f29f611c6..9ceb7a43b14 100644
--- a/openerp/fields.py
+++ b/openerp/fields.py
@@ -1749,10 +1749,10 @@ class Many2one(_Relational):
     def convert_to_display_name(self, value, record):
         return ustr(value.display_name)
 
-    def convert_to_onchange(self, value, fnames=None):
+    def convert_to_onchange(self, value, record, fnames=()):
         if not value.id:
             return False
-        return super(Many2one, self).convert_to_onchange(value, fnames)
+        return super(Many2one, self).convert_to_onchange(value, record, fnames)
 
 class UnionUpdate(SpecialValue):
     """ Placeholder for a value update; when this value is taken from the cache,