diff --git a/message/output/popup/mark_notification_read.php b/message/output/popup/mark_notification_read.php
index ad92b376c17..f2dd6096aa5 100644
--- a/message/output/popup/mark_notification_read.php
+++ b/message/output/popup/mark_notification_read.php
@@ -31,9 +31,14 @@ if (isguestuser()) {
 }
 
 $notificationid = required_param('notificationid', PARAM_INT);
-$redirecturl = optional_param('redirecturl', $CFG->wwwroot, PARAM_URL);
+$redirecturl = optional_param('redirecturl', '', PARAM_URL);
 $notification = $DB->get_record('notifications', array('id' => $notificationid));
 
+// If the redirect URL after filtering is empty, or it was never passed, then redirect to the notification page.
+if (empty($redirecturl)) {
+    $redirecturl = new moodle_url('/message/output/popup/notifications.php', ['notificationid' => $notificationid]);
+}
+
 // Check notification belongs to this user.
 if ($USER->id != $notification->useridto) {
     redirect($CFG->wwwroot);