diff --git a/lib/OpenLayers/Layer/Grid.js b/lib/OpenLayers/Layer/Grid.js
index 3852c30a2b..dc0a0f8320 100644
--- a/lib/OpenLayers/Layer/Grid.js
+++ b/lib/OpenLayers/Layer/Grid.js
@@ -886,7 +886,9 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
                     this.div.removeChild(this.backBuffer);
                     this.backBuffer = null;
                 }
-                this.lastResolution = this.getServerResolution();
+                if(this.map) {
+                    this.lastResolution = this.getServerResolution();
+                }
             }
         };
         tile.events.register("loadend", this, tile.onLoadEnd);