diff --git a/sys/boot/i386/loader/main.c b/sys/boot/i386/loader/main.c
index 2202c73d169..df11a2ef215 100644
--- a/sys/boot/i386/loader/main.c
+++ b/sys/boot/i386/loader/main.c
@@ -33,6 +33,7 @@ __FBSDID("$FreeBSD$");
  */
 
 #include <stand.h>
+#include <stddef.h>
 #include <string.h>
 #include <machine/bootinfo.h>
 #include <machine/psl.h>