diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 263dfd83f163..eef736cf34bc 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1859,13 +1859,12 @@ tcp_input(m, off0)
 					KASSERT(tp->t_dupacks == 1 ||
 					    tp->t_dupacks == 2,
 					    ("dupacks not 1 or 2"));
-					if (tp->t_dupacks == 1) {
+					if (tp->t_dupacks == 1)
 						tp->snd_limited = 0;
-						tp->snd_cwnd += tp->t_maxseg;
-					} else {
-						tp->snd_cwnd +=
-						    tp->t_maxseg * 2;
-					}
+					tp->snd_cwnd =
+					    (tp->snd_nxt - tp->snd_una) +
+					    (tp->t_dupacks - tp->snd_limited) *
+					    tp->t_maxseg;
 					(void) tcp_output(tp);
 					sent = tp->snd_max - oldsndmax;
 					if (sent > tp->t_maxseg) {
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 263dfd83f163..eef736cf34bc 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -1859,13 +1859,12 @@ tcp_input(m, off0)
 					KASSERT(tp->t_dupacks == 1 ||
 					    tp->t_dupacks == 2,
 					    ("dupacks not 1 or 2"));
-					if (tp->t_dupacks == 1) {
+					if (tp->t_dupacks == 1)
 						tp->snd_limited = 0;
-						tp->snd_cwnd += tp->t_maxseg;
-					} else {
-						tp->snd_cwnd +=
-						    tp->t_maxseg * 2;
-					}
+					tp->snd_cwnd =
+					    (tp->snd_nxt - tp->snd_una) +
+					    (tp->t_dupacks - tp->snd_limited) *
+					    tp->t_maxseg;
 					(void) tcp_output(tp);
 					sent = tp->snd_max - oldsndmax;
 					if (sent > tp->t_maxseg) {