diff --git a/addons/calendar/models/mail_activity_mixin.py b/addons/calendar/models/mail_activity_mixin.py
index 4e2b203bc76..e0f0eaed1b0 100644
--- a/addons/calendar/models/mail_activity_mixin.py
+++ b/addons/calendar/models/mail_activity_mixin.py
@@ -15,4 +15,4 @@ class MailActivityMixin(models.AbstractModel):
         """This computes the calendar event of the next activity.
         It evaluates to false if there is no such event."""
         for record in self:
-            record.activity_calendar_event_id = record.activity_ids[:1].calendar_event_id
+            record.activity_calendar_event_id = fields.first(record.activity_ids).calendar_event_id
diff --git a/addons/mail/models/mail_activity_mixin.py b/addons/mail/models/mail_activity_mixin.py
index 62f444a6c2f..b3c55903cb6 100644
--- a/addons/mail/models/mail_activity_mixin.py
+++ b/addons/mail/models/mail_activity_mixin.py
@@ -201,7 +201,7 @@ class MailActivityMixin(models.AbstractModel):
     @api.depends('activity_ids.date_deadline')
     def _compute_activity_date_deadline(self):
         for record in self:
-            record.activity_date_deadline = record.activity_ids[:1].date_deadline
+            record.activity_date_deadline = fields.first(record.activity_ids).date_deadline
 
     def _search_activity_date_deadline(self, operator, operand):
         if operator == '=' and not operand:
diff --git a/addons/test_mail/tests/test_performance.py b/addons/test_mail/tests/test_performance.py
index 64eca45c41b..7382c2a6be6 100644
--- a/addons/test_mail/tests/test_performance.py
+++ b/addons/test_mail/tests/test_performance.py
@@ -289,6 +289,24 @@ class TestBaseAPIPerformance(BaseMailPerformance):
         with self.assertQueryCount(admin=13, employee=13):
             activity.action_feedback(feedback='Zizisse Done !')
 
+    @warmup
+    def test_adv_activity_mixin_batched(self):
+        records = self.env['mail.test.activity'].create([{'name': 'Test'}] * 10)
+        MailActivity = self.env['mail.activity'].with_context({
+            'default_res_model': 'mail.test.activity',
+        })
+        activity_type = self.env.ref('mail.mail_activity_data_todo')
+
+        MailActivity.create([{
+            'summary': 'Test Activity',
+            'res_id': record.id,
+            'activity_type_id': activity_type.id,
+        } for record in records])
+
+        self.env.invalidate_all()
+        with self.assertQueryCount(3):
+            records.mapped('activity_date_deadline')
+
     @users('admin', 'employee')
     @warmup
     @mute_logger('odoo.models.unlink')