diff --git a/usr.bin/printf/printf.c b/usr.bin/printf/printf.c
index 3444c20264da..25acd157bacb 100644
--- a/usr.bin/printf/printf.c
+++ b/usr.bin/printf/printf.c
@@ -51,6 +51,7 @@ static char const sccsid[] = "@(#)printf.c	8.1 (Berkeley) 7/20/93";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #ifdef SHELL
 #define main printfcmd