Index: head/sys/netinet/tcp_input.c
===================================================================
--- head/sys/netinet/tcp_input.c
+++ head/sys/netinet/tcp_input.c
@@ -2010,7 +2010,8 @@
 			else
 				tp->t_flags |= TF_ACKNOW;
 
-			if ((thflags & TH_ECE) && V_tcp_do_ecn) {
+			if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
+			    V_tcp_do_ecn) {
 				tp->t_flags |= TF_ECN_PERMIT;
 				TCPSTAT_INC(tcps_ecn_shs);
 			}
Index: head/sys/netinet/tcp_stacks/rack.c
===================================================================
--- head/sys/netinet/tcp_stacks/rack.c
+++ head/sys/netinet/tcp_stacks/rack.c
@@ -5233,7 +5233,8 @@
 			tp->t_flags |= TF_ACKNOW;
 		}
 
-		if ((thflags & TH_ECE) && V_tcp_do_ecn) {
+		if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
+		    V_tcp_do_ecn) {
 			tp->t_flags |= TF_ECN_PERMIT;
 			TCPSTAT_INC(tcps_ecn_shs);
 		}