diff --git a/mail_template_attach_existing_attachment/wizard/mail_compose_message.py b/mail_template_attach_existing_attachment/wizard/mail_compose_message.py
index cf4d7b5e95..8db1dc1352 100644
--- a/mail_template_attach_existing_attachment/wizard/mail_compose_message.py
+++ b/mail_template_attach_existing_attachment/wizard/mail_compose_message.py
@@ -30,8 +30,8 @@ def _match_attachment(self, re_pattern, model, res_ids):
             )
         )
 
-    @api.onchange("template_id", "res_ids", "model")
-    def _compute_object_attachment_ids(self):
+    @api.depends("composition_mode", "model", "res_domain", "res_ids", "template_id")
+    def _compute_attachment_ids(self):
         for composer in self:
             composer.object_attachment_ids = self.env["ir.attachment"].browse()
             if (
@@ -43,8 +43,8 @@ def _compute_object_attachment_ids(self):
                     pattern, composer.model, parse_res_ids(composer.res_ids)
                 )
 
-    def get_mail_values(self, res_ids):
-        res = super().get_mail_values(res_ids)
+    def _prepare_mail_values_dynamic(self, res_ids):
+        res = super()._prepare_mail_values_dynamic(res_ids)
         self.ensure_one()
         if (
             self.template_id