diff --git a/lib/timeline/Core.js b/lib/timeline/Core.js
index c4a2f2f5..01204584 100644
--- a/lib/timeline/Core.js
+++ b/lib/timeline/Core.js
@@ -100,7 +100,7 @@ Core.prototype._create = function (container) {
   // create event listeners for all interesting events, these events will be
   // emitted via emitter
   this.hammer = Hammer(this.dom.root, {
-    prevent_default: true
+    preventDefault: true
   });
   this.listeners = {};
 
diff --git a/lib/timeline/Range.js b/lib/timeline/Range.js
index a9924b7e..f4dcf4ce 100644
--- a/lib/timeline/Range.js
+++ b/lib/timeline/Range.js
@@ -360,14 +360,18 @@ Range.prototype._onDrag = function (event) {
   if (!this.options.moveable) return;
   var direction = this.options.direction;
   validateDirection(direction);
+
   // refuse to drag when we where pinching to prevent the timeline make a jump
   // when releasing the fingers in opposite order from the touch screen
   if (!this.props.touch.allowDragging) return;
-  var delta = (direction == 'horizontal') ? event.gesture.deltaX : event.gesture.deltaY,
-      interval = (this.props.touch.end - this.props.touch.start),
-      width = (direction == 'horizontal') ? this.body.domProps.center.width : this.body.domProps.center.height,
-      diffRange = -delta / width * interval;
+
+  var delta = (direction == 'horizontal') ? event.gesture.deltaX : event.gesture.deltaY;
+  var interval = (this.props.touch.end - this.props.touch.start);
+  var width = (direction == 'horizontal') ? this.body.domProps.center.width : this.body.domProps.center.height;
+  var diffRange = -delta / width * interval;
   this._applyRange(this.props.touch.start + diffRange, this.props.touch.end + diffRange);
+
+  // fire a rangechange event
   this.body.emitter.emit('rangechange', {
     start: new Date(this.start),
     end:   new Date(this.end)
diff --git a/lib/timeline/component/ItemSet.js b/lib/timeline/component/ItemSet.js
index 9675637b..6feb7e2c 100644
--- a/lib/timeline/component/ItemSet.js
+++ b/lib/timeline/component/ItemSet.js
@@ -48,10 +48,10 @@ function ItemSet(body, options) {
     onMove: function (item, callback) {
       callback(item);
     },
-    onMoving: null,
     onRemove: function (item, callback) {
       callback(item);
     },
+    onMoving: null,  // onMoving is null by default for better performance (other on* functions do not support null)
 
     margin: {
       item: {
@@ -299,8 +299,8 @@ ItemSet.prototype.setOptions = function(options) {
 
     // callback functions
     var addCallback = (function (name) {
-      if (name in options) {
-        var fn = options[name];
+      var fn = options[name];
+      if (fn) {
         if (!(fn instanceof Function)) {
           throw new Error('option ' + name + ' must be a function ' + name + '(item, callback)');
         }
@@ -1157,6 +1157,7 @@ ItemSet.prototype._onDrag = function (event) {
  * @private
  */
 ItemSet.prototype._updateItemProps = function(item, props) {
+  // TODO: copy all properties from props to item? (also new ones)
   if ('start' in props) item.data.start = props.start;
   if ('end' in props)   item.data.end   = props.end;
   if ('group' in props && item.data.group != props.group) {