diff --git a/sys/lib/Makefile b/sys/lib/Makefile
index 0b5999e64a83..6e9c6f1ef8ce 100644
--- a/sys/lib/Makefile
+++ b/sys/lib/Makefile
@@ -1,5 +1,13 @@
-#	$Id: Makefile,v 1.2 1993/10/13 10:58:41 cgd Exp $
+#	$Id: Makefile,v 1.3 1993/12/04 03:13:31 cgd Exp $
 
-SUBDIR+= libc_sa libkern libnetboot
+.if exists(libc_sa)
+SUBDIR+= libc_sa
+.endif
+.if exists(libkern)
+SUBDIR+= libkern
+.endif
+.if exists(libnetboot)
+SUBDIR+= libnetboot
+.endif
 
 .include <bsd.subdir.mk>