diff --git a/addons/event/models/event_registration.py b/addons/event/models/event_registration.py
index 27da716a968..74c320b6dde 100644
--- a/addons/event/models/event_registration.py
+++ b/addons/event/models/event_registration.py
@@ -235,7 +235,7 @@ class EventRegistration(models.Model):
             default_model='event.registration',
             default_res_id=self.id,
             default_use_template=bool(template),
-            default_template_ref='mail.template,%i' % template.id,
+            default_template_id=template.id,
             default_composition_mode='comment',
             custom_layout="mail.mail_notification_light",
         )