diff --git a/VERSION b/VERSION
index f7281edd..fe40e0e2 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-Version 2.4.6-stable+timestamp.2013.05.03.22.24.45
+Version 2.4.6-stable+timestamp.2013.05.04.10.23.42
diff --git a/gluon/dal.py b/gluon/dal.py
index ffc599ed..39ebdad2 100644
--- a/gluon/dal.py
+++ b/gluon/dal.py
@@ -9744,7 +9744,9 @@ class Set(object):
         return '<Set %s>' % BaseAdapter.expand(self.db._adapter,self.query)
 
     def __call__(self, query, ignore_common_filters=False):
-        if isinstance(query,Table):
+        if query is None:
+            return self
+        elif isinstance(query,Table):
             query = self.db._adapter.id_query(query)
         elif isinstance(query,str):
             query = Expression(self.db,query)