Typo (missing _) in _xdr line.
diff --git a/Modules/Setup.in b/Modules/Setup.in
index 505aa60..6538cd4 100644
--- a/Modules/Setup.in
+++ b/Modules/Setup.in
@@ -139,7 +139,7 @@
 #dbm dbmmodule.c 	# dbm(3) may require -lndbm or similar
 #nis nismodule.c 	# Sun yellow pages -- not everywhere
 #termios termios.c	# Steen Lumholt's termios module
-#_xdr xdrmodule.c # -lnsl # Helper for xdrlib.py
+#_xdr _xdrmodule.c # -lnsl # Helper for xdrlib.py
 
 
 # Multimedia modules -- on by default.