diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 1b9f7554a400..fc4afec6a5e5 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
- *	$Id: tcp_input.c,v 1.60 1997/08/16 19:15:39 wollman Exp $
+ *	$Id: tcp_input.c,v 1.61 1997/09/16 18:36:05 joerg Exp $
  */
 
 #include "opt_tcpdebug.h"
@@ -808,15 +808,17 @@ findpcb:
 			 * option, check it to make sure this segment really
 			 * matches our SYN.  If not, just drop it as old
 			 * duplicate, but send an RST if we're still playing
-			 * by the old rules.
+			 * by the old rules.  If no CC.ECHO option, make sure
+			 * we don't get fooled into using T/TCP.
 			 */
-			if ((to.to_flag & TOF_CCECHO) &&
-			    tp->cc_send != to.to_ccecho) {
-				if (taop->tao_ccsent != 0)
-					goto drop;
-				else
-					goto dropwithreset;
-			}
+			if (to.to_flag & TOF_CCECHO) {
+				if (tp->cc_send != to.to_ccecho)
+					if (taop->tao_ccsent != 0)
+						goto drop;
+					else
+						goto dropwithreset;
+			} else
+				tp->t_flags &= ~TF_RCVD_CC;
 			tcpstat.tcps_connects++;
 			soisconnected(so);
 			/* Do window scaling on this connection? */
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 1b9f7554a400..fc4afec6a5e5 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)tcp_input.c	8.12 (Berkeley) 5/24/95
- *	$Id: tcp_input.c,v 1.60 1997/08/16 19:15:39 wollman Exp $
+ *	$Id: tcp_input.c,v 1.61 1997/09/16 18:36:05 joerg Exp $
  */
 
 #include "opt_tcpdebug.h"
@@ -808,15 +808,17 @@ findpcb:
 			 * option, check it to make sure this segment really
 			 * matches our SYN.  If not, just drop it as old
 			 * duplicate, but send an RST if we're still playing
-			 * by the old rules.
+			 * by the old rules.  If no CC.ECHO option, make sure
+			 * we don't get fooled into using T/TCP.
 			 */
-			if ((to.to_flag & TOF_CCECHO) &&
-			    tp->cc_send != to.to_ccecho) {
-				if (taop->tao_ccsent != 0)
-					goto drop;
-				else
-					goto dropwithreset;
-			}
+			if (to.to_flag & TOF_CCECHO) {
+				if (tp->cc_send != to.to_ccecho)
+					if (taop->tao_ccsent != 0)
+						goto drop;
+					else
+						goto dropwithreset;
+			} else
+				tp->t_flags &= ~TF_RCVD_CC;
 			tcpstat.tcps_connects++;
 			soisconnected(so);
 			/* Do window scaling on this connection? */