diff --git a/lib/OpenLayers/Control/MouseToolbar.js b/lib/OpenLayers/Control/MouseToolbar.js
index 309660a871..712e59c3d5 100644
--- a/lib/OpenLayers/Control/MouseToolbar.js
+++ b/lib/OpenLayers/Control/MouseToolbar.js
@@ -180,7 +180,7 @@ OpenLayers.Control.MouseToolbar.prototype =
 
     switchModeTo: function(mode) {
         if (mode != this.mode) {
-            if (this.mode) {
+            if (this.mode && this.buttons[this.mode]) {
                 OpenLayers.Util.modifyAlphaImageDiv(this.buttons[this.mode], null, null, null, this.buttons[this.mode].imgLocation);
             }
             if (this.mode == "measure" && mode != "measure") {
@@ -193,7 +193,9 @@ OpenLayers.Control.MouseToolbar.prototype =
                 this.measureStart = null;
             }
             this.mode = mode;
-            OpenLayers.Util.modifyAlphaImageDiv(this.buttons[mode], null, null, null, this.buttons[mode].activeImgLocation);
+            if (this.buttons[mode]) {
+                OpenLayers.Util.modifyAlphaImageDiv(this.buttons[mode], null, null, null, this.buttons[mode].activeImgLocation);
+            }
         } 
     },