diff --git a/include/ar.h b/include/ar.h
index e04874fcbda3..40b4d74b04c6 100644
--- a/include/ar.h
+++ b/include/ar.h
@@ -39,11 +39,15 @@
  * SUCH DAMAGE.
  *
  *	@(#)ar.h	8.2 (Berkeley) 1/21/94
+ *
+ * $FreeBSD$
  */
 
 #ifndef _AR_H_
 #define	_AR_H_
 
+#include <sys/cdefs.h>
+
 /* Pre-4BSD archives had these magic numbers in them. */
 #define	OARMAG1	0177555
 #define	OARMAG2	0177545
@@ -62,6 +66,6 @@ struct ar_hdr {
 	char ar_size[10];		/* size in bytes */
 #define	ARFMAG	"`\n"
 	char ar_fmag[2];		/* consistency check */
-};
+} __packed;
 
 #endif /* !_AR_H_ */