diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 4353b7750e7..0bf5be4ec96 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -357,6 +357,8 @@ struct tcptw {
 	u_int		t_starttime;
 	int		tw_time;
 	TAILQ_ENTRY(tcptw) tw_2msl;
+	void		*tw_pspare;	/* TCP_SIGNATURE */
+	u_int		*tw_spare;	/* TCP_SIGNATURE */
 };
 
 #define	intotcpcb(ip)	((struct tcpcb *)(ip)->inp_ppcb)