diff --git a/lib/utils.js b/lib/utils.js
index 7797b068530..799a6a2b4ee 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -120,6 +120,7 @@ exports.contentDisposition = deprecate.function(contentDisposition,
  * also includes `.originalIndex` for stable sorting
  *
  * @param {String} str
+ * @param {Number} index
  * @return {Object}
  * @api private
  */