diff --git a/lib/OpenLayers/Strategy/Cluster.js b/lib/OpenLayers/Strategy/Cluster.js
index 3063d117d7..9fac5c698f 100644
--- a/lib/OpenLayers/Strategy/Cluster.js
+++ b/lib/OpenLayers/Strategy/Cluster.js
@@ -140,7 +140,7 @@ OpenLayers.Strategy.Cluster = OpenLayers.Class(OpenLayers.Strategy, {
      */
     cluster: function() {
         if(this.features) {
-            var resolution = this.layer.getResolution();
+            var resolution = this.layer.map.getResolution();
             if(resolution != this.resolution || !this.clustersExist()) {
                 this.resolution = resolution;
                 var clusters = [];