diff --git a/addons/event_sale/event_sale.py b/addons/event_sale/event_sale.py
index 8abe4a471ec..d37ff61a861 100644
--- a/addons/event_sale/event_sale.py
+++ b/addons/event_sale/event_sale.py
@@ -38,6 +38,7 @@ class sale_order_line(osv.osv):
     _inherit = 'sale.order.line'
     _columns = {
         'event': fields.many2one('event.event', 'Event', help="Choose an event and it will authomaticaly create a registration for this event"),
+        #those 2 fields are used for dynamic domains and filled by onchange
         'event_type_id': fields.related('event_type_id', type='many2one', relation="event.type", string="Event Type"),
         'event_ok': fields.related('event_ok', string='event_ok', type='boolean'),
     }