--- a/cwconfig.py	Wed Jun 02 14:36:54 2010 +0200
+++ b/cwconfig.py	Wed Jun 02 14:48:36 2010 +0200
@@ -1156,7 +1156,7 @@
         def as_sql(self, backend, args):
             raise NotImplementedError('source only callback')
 
-        def source_execute(self, source, value):
+        def source_execute(self, source, session, value):
             fpath = source.binary_to_str(value)
             try:
                 return Binary(fpath)