diff --git a/www/media/osm_map.js b/www/media/osm_map.js
index d4622e6..d88149c 100644
--- a/www/media/osm_map.js
+++ b/www/media/osm_map.js
@@ -152,7 +152,9 @@ function mapInit()
     OpenLayers.Util.extend(selectControl, {
         draw: function() {
             this.box = new OpenLayers.Handler.Box(selectControl,
-                {'done': this.notice}, {keyMask: OpenLayers.Handler.MOD_CTRL});
+                {'done': this.notice}, 
+                {keyMask: ( navigator.platform.match(/Mac/) ? 
+                            OpenLayers.Handler.MOD_ALT : OpenLayers.Handler.MOD_CTRL )});
             this.box.activate();
         },