Index: Python-2.5.1/Lib/distutils/command/build_ext.py
===================================================================
--- Python-2.5.1.orig/Lib/distutils/command/build_ext.py
+++ Python-2.5.1/Lib/distutils/command/build_ext.py
@@ -513,7 +513,7 @@ class build_ext (Command):
             target_lang=language)
 
 
-    def swig_sources (self, sources, extension):
+    def swig_sources (self, sources, extension=None):
 
         """Walk the list of source files in 'sources', looking for SWIG
         interface (.i) files.  Run SWIG on all that are found, and