diff --git a/sys/sys/un.h b/sys/sys/un.h
index 42a8b4851c96..65d246b60dea 100644
--- a/sys/sys/un.h
+++ b/sys/sys/un.h
@@ -49,7 +49,7 @@ typedef	_BSD_SA_FAMILY_T_	sa_family_t;
  * Definitions for UNIX IPC domain.
  */
 struct sockaddr_un {
-	u_char	sun_len;		/* sockaddr len including null */
+	unsigned char	sun_len;	/* sockaddr len including null */
 	sa_family_t	sun_family;	/* AF_UNIX */
 	char	sun_path[104];		/* path name (gag) */
 };