diff --git a/lang/en/message.php b/lang/en/message.php
index 220477b479a..a33f24dfe8f 100644
--- a/lang/en/message.php
+++ b/lang/en/message.php
@@ -84,6 +84,7 @@ $string['nomessagesfound'] = 'No messages were found';
 $string['noreply'] = 'Do not reply to this message';
 $string['noncontacts'] = 'Non-contacts';
 $string['nonotifications'] = 'You have no notifications';
+$string['notificationdatahasnotbeenmigrated'] = 'Your notifications are temporarily unavailable due to upgrades in the notification infrastructure. Please wait for them to be migrated.';
 $string['notificationwindow'] = 'Notification window';
 $string['notificationpreferences'] = 'Notification preferences';
 $string['notificationimage'] = 'Notification image';
diff --git a/message/output/popup/notifications.php b/message/output/popup/notifications.php
index 2f0bc2581fd..a33ffe62937 100644
--- a/message/output/popup/notifications.php
+++ b/message/output/popup/notifications.php
@@ -65,6 +65,14 @@ $context = [
 
 echo $OUTPUT->header();
 echo $OUTPUT->heading(get_string('notifications', 'message'));
+
+// Display a message if the notifications have not been migrated yet.
+if (!get_user_preferences('core_message_migrate_data', false, $userid)) {
+    $notify = new \core\output\notification(get_string('notificationdatahasnotbeenmigrated', 'message'),
+        \core\output\notification::NOTIFY_WARNING);
+    echo $OUTPUT->render($notify);
+}
+
 echo $renderer->render_from_template('message_popup/notification_area', $context);
 echo $OUTPUT->footer();