diff --git a/openupgrade_scripts/scripts/mail/16.0.1.10/end-migration.py b/openupgrade_scripts/scripts/mail/16.0.1.10/end-migration.py
new file mode 100644
index 000000000000..a44daaffa61e
--- /dev/null
+++ b/openupgrade_scripts/scripts/mail/16.0.1.10/end-migration.py
@@ -0,0 +1,69 @@
+# SPDX-FileCopyrightText: 2024 Coop IT Easy SC
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+import os.path
+
+from lxml import etree
+from openupgradelib import openupgrade
+
+from odoo.modules import get_manifest
+from odoo.tools.misc import file_open
+
+
+def is_xml_filename(filename):
+    return os.path.splitext(filename)[1].lower() == ".xml"
+
+
+def get_module_xml_files(module_name):
+    return filter(is_xml_filename, get_manifest(module_name).get("data", []))
+
+
+def find_record_data_path(model_name, module_name, xml_id):
+    """
+    Get the path of the XML data file containing the record.
+    """
+    for xml_file in get_module_xml_files(module_name):
+        filepath = "/".join((module_name, xml_file))
+        with file_open(filepath, "rb") as f:
+            root = etree.parse(f)
+            found = root.xpath(
+                '//record[@model="{model_name}"][@id="{xml_id}"]'.format(
+                    model_name=model_name, xml_id=xml_id
+                )
+            )
+            if found:
+                return filepath
+    return None
+
+
+def fill_all_null_mail_template_template_fs(env):
+    """
+    Fill the new template_fs field of all mail.template if it is null.
+
+    The mail.template template_fs field must contain the path of the data file
+    where it is defined (to allow for it to be reset to its default value).
+    Fill empty values by searching for the mail templates (by xml id) in the
+    XML files of the module that defines it.
+    """
+    env.cr.execute(
+        """
+        select mt.id, imd.module, imd.name
+        from mail_template as mt
+        inner join ir_model_data as imd on
+            imd.model = 'mail.template' and
+            imd.res_id = mt.id
+        where mt.template_fs is null
+        """
+    )
+    mail_template_model = env["mail.template"]
+    for mail_template_id, module_name, template_name in env.cr.fetchall():
+        template_fs = find_record_data_path("mail.template", module_name, template_name)
+        if template_fs is not None:
+            mail_template = mail_template_model.browse(mail_template_id)
+            mail_template.template_fs = template_fs
+
+
+@openupgrade.migrate()
+def migrate(env, version):
+    fill_all_null_mail_template_template_fs(env)
diff --git a/openupgrade_scripts/scripts/mail/16.0.1.10/upgrade_analysis_work.txt b/openupgrade_scripts/scripts/mail/16.0.1.10/upgrade_analysis_work.txt
index 61fb9779eece..df636bd0b1e8 100644
--- a/openupgrade_scripts/scripts/mail/16.0.1.10/upgrade_analysis_work.txt
+++ b/openupgrade_scripts/scripts/mail/16.0.1.10/upgrade_analysis_work.txt
@@ -86,9 +86,11 @@ mail         / mail.template            / model_object_field (many2one) : DEL re
 mail         / mail.template            / null_value (char)             : DEL
 mail         / mail.template            / sub_model_object_field (many2one): DEL relation: ir.model.fields
 mail         / mail.template            / sub_object (many2one)         : DEL relation: ir.model
-mail         / mail.template            / template_fs (char)            : NEW
 # NOTHING TO DO
 
+mail         / mail.template            / template_fs (char)            : NEW
+# DONE (end-migration): fill the new field
+
 
 mail         / res.partner              / channel_ids (many2many)       : table is now 'mail_channel_member' ('mail_channel_partner')
 # DONE in pre-migration script when renaming the model