Index: tcp_syncache.c
===================================================================
--- tcp_syncache.c
+++ tcp_syncache.c
@@ -1668,7 +1668,8 @@
 		sc->sc_peer_mss = to->to_mss;	/* peer mss may be zero */
 	if (ltflags & TF_NOOPT)
 		sc->sc_flags |= SCF_NOOPT;
-	if ((th->th_flags & (TH_ECE|TH_CWR)) && V_tcp_do_ecn)
+	if (((th->th_flags & (TH_ECE|TH_CWR)) == (TH_ECE|TH_CWR)) &&
+	    V_tcp_do_ecn)
 		sc->sc_flags |= SCF_ECN;
 
 	if (V_tcp_syncookies)