diff -rupN a/utils/ndptool.c b/utils/ndptool.c
--- a/utils/ndptool.c	2017-07-09 02:25:46.731106571 -0500
+++ b/utils/ndptool.c	2017-07-09 02:28:40.426675110 -0500
@@ -27,6 +27,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <errno.h>
+#include <sys/select.h>
 #include <ndp.h>
 
 enum verbosity_level {