diff --git a/addons/calendar/models/mail_activity.py b/addons/calendar/models/mail_activity.py
index 3efcea70a3b..4cf142ed42d 100644
--- a/addons/calendar/models/mail_activity.py
+++ b/addons/calendar/models/mail_activity.py
@@ -23,7 +23,7 @@ class MailActivity(models.Model):
             'default_activity_type_id': self.activity_type_id.id,
             'default_res_id': self.env.context.get('default_res_id'),
             'default_res_model': self.env.context.get('default_res_model'),
-            'default_name': self.summary,
+            'default_name': self.summary or self.res_name,
             'default_description': self.note and tools.html2plaintext(self.note) or '',
             'default_activity_ids': [(6, 0, self.ids)],
         }