Index: fb_url_rewrite.inc
===================================================================
--- fb_url_rewrite.inc	(revision 8592)
+++ fb_url_rewrite.inc	(working copy)
@@ -91,7 +91,9 @@
   function custom_url_rewrite_outbound(&$path, &$options, $original_path) {
     if (function_exists('fb_canvas_url_outbound_alter'))
       fb_canvas_url_outbound_alter($path, $options, $original_path);
-    fb_url_outbound_alter($path, $options, $original_path);
+    if (!$options['off_canvas']) {
+      fb_url_outbound_alter($path, $options, $original_path);
+    }
   }
 }