diff --git a/lib/response.js b/lib/response.js
index c98986f..1c10068 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -248,7 +248,7 @@ module.exports = {
    *    this.redirect('http://google.com');
    *
    * @param {String} url
-   * @param {String} alt
+   * @param {String} [alt]
    * @api public
    */