Of course, you meant "#if 0" and not "#ifdef 0". :)
diff --git a/Include/pyport.h b/Include/pyport.h
index dceb98d..c682680 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -281,7 +281,7 @@
 /* If the fd manipulation macros aren't defined,
    here is a set that should do the job */
 
-#ifdef 0 /* disabled and probably obsolete */
+#if 0 /* disabled and probably obsolete */
 
 #ifndef	FD_SETSIZE
 #define	FD_SETSIZE	256