--- a/urltree.py	Mon Feb 09 06:55:51 2009 +0200
+++ b/urltree.py	Tue Feb 10 01:07:15 2009 +0200
@@ -588,7 +588,7 @@
                 value = type.parse(value)
 
             # set default?
-            if not value :
+            if value is None :
                 if default :
                     value = default