diff --git a/lib/timeline/component/ItemSet.js b/lib/timeline/component/ItemSet.js
index 485c5fe2..5e615b7a 100644
--- a/lib/timeline/component/ItemSet.js
+++ b/lib/timeline/component/ItemSet.js
@@ -541,6 +541,7 @@ ItemSet.prototype.show = function() {
 
 /**
  * Activates the popup timer to show the given popup after a fixed time.
+ * @param {any} popup
  */
 ItemSet.prototype.setPopupTimer = function (popup) {
     this.clearPopupTimer();