diff --git a/lib/OpenLayers/Control/OverviewMap.js b/lib/OpenLayers/Control/OverviewMap.js
index 20b70eb4d0..5786882ea7 100644
--- a/lib/OpenLayers/Control/OverviewMap.js
+++ b/lib/OpenLayers/Control/OverviewMap.js
@@ -428,12 +428,14 @@ OpenLayers.Control.OverviewMap.prototype =
         // The base layer for overview map needs to be in the same projection
         // as the base layer for the main map.  This should be made more robust.
         if(this.map.units != 'degrees') {
-            if(this.map.getProjection() != this.ovmap.getProjection()) {
+            if(this.ovmap.getProjection() && (this.map.getProjection() != this.ovmap.getProjection())) {
                 alert('The overview map only works when it is in the same projection as the main map');
             }
         }
         var pxBounds = this.getRectBoundsFromMapBounds(this.map.getExtent());
-        this.setRectPxBounds(pxBounds);
+        if (pxBounds) {
+          this.setRectPxBounds(pxBounds);
+        }
     },
     
     /**
@@ -489,8 +491,12 @@ OpenLayers.Control.OverviewMap.prototype =
                                                    lonLatBounds.top);
         var leftBottomPx = this.getOverviewPxFromLonLat(leftBottomLonLat);
         var rightTopPx = this.getOverviewPxFromLonLat(rightTopLonLat);
-        return new OpenLayers.Bounds(leftBottomPx.x, leftBottomPx.y,
-                                     rightTopPx.x, rightTopPx.y);
+        var bounds = null;
+        if (leftBottomPx && rightTopPx) {
+            bounds = new OpenLayers.Bounds(leftBottomPx.x, leftBottomPx.y,
+                                           rightTopPx.x, rightTopPx.y);
+        }
+        return bounds;
     },
 
     /**
@@ -540,10 +546,13 @@ OpenLayers.Control.OverviewMap.prototype =
     getOverviewPxFromLonLat: function(lonlat) {
         var res  = this.ovmap.getResolution();
         var extent = this.ovmap.getExtent();
-        return new OpenLayers.Pixel(
-                       Math.round(1/res * (lonlat.lon - extent.left)),
-                       Math.round(1/res * (extent.top - lonlat.lat))
-                       );
+        var px = null;
+        if (extent) {
+            px = new OpenLayers.Pixel(
+                        Math.round(1/res * (lonlat.lon - extent.left)),
+                        Math.round(1/res * (extent.top - lonlat.lat)));
+        } 
+        return px;
     },
 
     /** @final @type String */