diff --git a/lib/timeline/component/ItemSet.js b/lib/timeline/component/ItemSet.js
index 31232bc9..94c5a3c8 100644
--- a/lib/timeline/component/ItemSet.js
+++ b/lib/timeline/component/ItemSet.js
@@ -1343,7 +1343,7 @@ ItemSet.prototype._onAddItem = function (event) {
     var itemData = me.itemsData.get(item.id); // get a clone of the data from the dataset
     this.options.onUpdate(itemData, function (itemData) {
       if (itemData) {
-        me.itemsData.update(itemData);
+        me.itemsData.getDataSet().update(itemData);
       }
     });
   }
@@ -1373,7 +1373,7 @@ ItemSet.prototype._onAddItem = function (event) {
     // execute async handler to customize (or cancel) adding an item
     this.options.onAdd(newItem, function (item) {
       if (item) {
-        me.itemsData.add(item);
+        me.itemsData.getDataSet().add(item);
         // TODO: need to trigger a redraw?
       }
     });