diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index 52a2ab4e3a..8e7606c086 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -931,7 +931,11 @@ OpenLayers.Map.prototype = {
     * @private
     */
     getLonLatFromViewPortPx: function (viewPortPx) {
-        return this.baseLayer.getLonLatFromViewPortPx(viewPortPx);
+        var lonlat = null; 
+        if (this.baseLayer != null) {
+            lonlat = this.baseLayer.getLonLatFromViewPortPx(viewPortPx);
+        }
+        return lonlat;
     },
 
     /**
@@ -944,7 +948,11 @@ OpenLayers.Map.prototype = {
     * @private
     */
     getViewPortPxFromLonLat: function (lonlat) {
-        return this.baseLayer.getViewPortPxFromLonLat(lonlat);
+        var px = null; 
+        if (this.baseLayer != null) {
+            px = this.baseLayer.getViewPortPxFromLonLat(lonlat);
+        }
+        return px;
     },