diff --git a/lib/OpenLayers/Layer/WorldWind.js b/lib/OpenLayers/Layer/WorldWind.js
index 76a19f179c..1adeedcce2 100644
--- a/lib/OpenLayers/Layer/WorldWind.js
+++ b/lib/OpenLayers/Layer/WorldWind.js
@@ -58,7 +58,7 @@ OpenLayers.Layer.WorldWind.prototype =
     getZoom: function () {
         var zoom = this.map.getZoom();
         var extent = this.map.getMaxExtent();
-        zoom = zoom - Math.log(this.map.maxResolution / (this.lzd/512))/Math.log(2);
+        zoom = zoom - Math.log(this.maxResolution / (this.lzd/512))/Math.log(2);
         return zoom;
     },
 
@@ -71,6 +71,8 @@ OpenLayers.Layer.WorldWind.prototype =
      * @type String
      */
     getURL: function (bounds) {
+        var zoom = this.getZoom();
+        var extent = this.map.getMaxExtent();
         var deg = this.lzd/Math.pow(2,this.getZoom());
         var x = Math.floor((bounds.left - extent.left)/deg);
         var y = Math.floor((bounds.bottom - extent.bottom)/deg);