diff --git a/src/MoveableMarker.js b/src/MoveableMarker.js
index f37c358..66731aa 100644
--- a/src/MoveableMarker.js
+++ b/src/MoveableMarker.js
@@ -4,12 +4,9 @@ L.Playback.MoveableMarker = L.Marker.extend({
     initialize: function (startLatLng, options, feature) {    
         var marker_options = options.marker || {};
 
-        if (jQuery.isFunction(marker_options)){        
+        if (typeof(marker_options)=== 'function'){        
             marker_options = marker_options(feature);
         }
-        
-        L.Marker.prototype.initialize.call(this, startLatLng, marker_options);
-        
         this.popupContent = '';
         this.feature = feature;
 		
diff --git a/src/TracksLayer.js b/src/TracksLayer.js
index 87bd4c3..c91cf34 100644
--- a/src/TracksLayer.js
+++ b/src/TracksLayer.js
@@ -7,7 +7,7 @@ L.Playback.TracksLayer = L.Class.extend({
     initialize : function (map, options) {
         var layer_options = options.layer || {};
         
-        if (jQuery.isFunction(layer_options)){
+        if (typeof(layer_options) === 'function') {
             layer_options = layer_options(feature);
         }