diff --git a/usr.bin/asa/asa.c b/usr.bin/asa/asa.c
index 8e2b2d7f953b..95cb588a052e 100644
--- a/usr.bin/asa/asa.c
+++ b/usr.bin/asa/asa.c
@@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$");
 #include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 static void asa(FILE *);
 static void usage(void);