diff --git a/project_ux/models/__init__.py b/project_ux/models/__init__.py
index c6141a05..e3af6818 100644
--- a/project_ux/models/__init__.py
+++ b/project_ux/models/__init__.py
@@ -5,3 +5,4 @@
 ##############################################################################
 from . import project_task_type
 from . import project_task
+from . import mail_followers
diff --git a/project_ux/models/mail_followers.py b/project_ux/models/mail_followers.py
new file mode 100644
index 00000000..2abb69c4
--- /dev/null
+++ b/project_ux/models/mail_followers.py
@@ -0,0 +1,16 @@
+from odoo import models
+from odoo.tools.sql import create_index
+
+
+class MailFollowers(models.Model):
+    _inherit = "mail.followers"
+
+    def init(self):
+        super().init()
+        create_index(  # used by the project.task record rules on followers
+            self.env.cr,
+            indexname="mail_followers_project_task_partner_id_res_id_index",
+            tablename=self._table,
+            expressions=["partner_id", "res_id"],
+            where="res_model = 'project.task'",
+        )