diff --git a/lib/OpenLayers/Layer/Bing.js b/lib/OpenLayers/Layer/Bing.js
index 8945662fe1..638891dadb 100644
--- a/lib/OpenLayers/Layer/Bing.js
+++ b/lib/OpenLayers/Layer/Bing.js
@@ -106,9 +106,10 @@ OpenLayers.Layer.Bing = OpenLayers.Class(OpenLayers.Layer.XYZ, {
      *  this is undocumented and the Imagery Metadata API always returns HTTP
      *  urls.
      *
-     *  Default is
+     *  Default is '', unless when executed from a file:/// uri, in which case
+     *  it is 'http:'.
      */
-    protocol: '',
+    protocol: ~window.location.href.indexOf('http') ? '' : 'http:',
 
     /**
      * Constructor: OpenLayers.Layer.Bing