--- rblcheck.c.orig	Sat Sep 10 12:09:30 2016
+++ rblcheck.c	Sat Sep 10 12:09:50 2016
@@ -32,6 +32,7 @@
 #else
 # include <unistd.h>
 # include <sys/types.h>
+# include <sys/select.h> /* fd_set */
 # include <sys/socket.h>
 # include <netinet/in.h>
 #endif