diff --git a/include/net/tcp.h b/include/net/tcp.h
index e07878d..bc7c134 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -214,6 +214,7 @@
 
 /* Bit Flags for sysctl_tcp_fastopen */
 #define	TFO_CLIENT_ENABLE	1
+#define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
 
 extern struct inet_timewait_death_row tcp_death_row;