diff --git a/lib/rhino/wormhole.rb b/lib/rhino/wormhole.rb
index fdf9845..94b4540 100644
--- a/lib/rhino/wormhole.rb
+++ b/lib/rhino/wormhole.rb
@@ -1,11 +1,13 @@
 
 module Rhino
-  module To    
+  module To        
+    JS_UNDEF = [J::Scriptable::NOT_FOUND, J::Undefined]
+    
     def ruby(object)
       case object
-      when J::Scriptable::NOT_FOUND then nil
-      when J::Wrapper               then object.unwrap
-      when J::Scriptable            then NativeObject.new(object)
+      when *JS_UNDEF      then nil
+      when J::Wrapper     then object.unwrap
+      when J::Scriptable  then NativeObject.new(object)
       else  object
       end        
     end
diff --git a/spec/rhino/wormhole_spec.rb b/spec/rhino/wormhole_spec.rb
index db14034..29d1ce5 100644
--- a/spec/rhino/wormhole_spec.rb
+++ b/spec/rhino/wormhole_spec.rb
@@ -33,6 +33,10 @@ describe Rhino::To do
         end
       end
     end
+    
+    it "converts javascript undefined into nil" do
+      To.ruby(J::Undefined.instance).should be_nil
+    end
   end
   
   describe  "javascript translation" do