--- a/urltree.py	Mon Feb 16 20:07:45 2009 +0200
+++ b/urltree.py	Mon Feb 16 20:56:05 2009 +0200
@@ -615,18 +615,21 @@
             else :
                 # parse value
                 value = type.parse(value)
-
+            
+            # XXX: this should set it to True or something... it's a flag, "/foo?bar"
             # set default?
             if value is None :
-                if default :
-                    value = default
-
                 if default == '' :
                     # do not pass key at all
                     continue
 
-                # otherwise, fail
-                raise URLError("No value given for required argument: %r" % (key, ))
+                elif default is not None :
+                    # pass default value
+                    value = default
+
+                else :
+                    # required arg, no default
+                    raise URLError("No value given for required argument: %r" % (key, ))
             
             # already have a non-default value?
             if key in kwargs and key not in default_labels :