diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index da4dcd9670..e894727d48 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -96,6 +96,8 @@ OpenLayers.Map.prototype = {
 
         this.popups = new Array();
 
+        this.updateSize();
+
         // always call map.destroy()
         Event.observe(window, 'unload', 
             this.destroy.bindAsEventListener(this));
@@ -198,18 +200,19 @@ OpenLayers.Map.prototype = {
     * @returns {OpenLayers.Size}
     */
     getSize: function () {
-        // should this be cached?
-        var size = new OpenLayers.Size(
+        return this.size;
+    },
+
+    updateSize: function() {
+        this.size = new OpenLayers.Size(
                     this.div.clientWidth, this.div.clientHeight);
         
         // Workaround for the fact that hidden elements return 0 for size.
-        if (size.w == 0 && size.h == 0) {
-            size.w = parseInt(this.div.style.width);
-            size.h = parseInt(this.div.style.height);
+        if (this.size.w == 0 && this.size.h == 0) {
+            this.size.w = parseInt(this.div.style.width);
+            this.size.h = parseInt(this.div.style.height);
         }
-        return size;
     },
-
     /**
     * @return {OpenLayers.LonLat}
     */