diff --git a/lib/response.js b/lib/response.js
index 4d79650..d9949fa 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -247,7 +247,7 @@ module.exports = {
    *    this.redirect('http://google.com');
    *
    * @param {String} url
-   * @param {String} alt
+   * @param {String} [alt]
    * @api public
    */