diff --git a/cron.py b/cron.py
index 56ad59de..094681f5 100644
--- a/cron.py
+++ b/cron.py
@@ -590,7 +590,8 @@ def sanity_check():
                         mailbox.user.email,
                         f"Mailbox {mailbox.email} is disabled",
                         render(
-                            "transactional/disable-mailbox-warning.txt", mailbox=mailbox
+                            "transactional/disable-mailbox-warning.txt.jinja2",
+                            mailbox=mailbox,
                         ),
                         render(
                             "transactional/disable-mailbox-warning.html",
diff --git a/templates/emails/transactional/disable-mailbox-warning.txt b/templates/emails/transactional/disable-mailbox-warning.txt.jinja2
similarity index 100%
rename from templates/emails/transactional/disable-mailbox-warning.txt
rename to templates/emails/transactional/disable-mailbox-warning.txt.jinja2