diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 226be181dfd..446fe9ff1c8 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1023,6 +1023,7 @@ after_listen:
 				tcpstat.tcps_rcvackbyte += acked;
 				sbdrop(&so->so_snd, acked);
 				tp->snd_una = th->th_ack;
+				tp->t_dupacks = 0;
 				m_freem(m);
 				ND6_HINT(tp); /* some progress has been done */
 
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 226be181dfd..446fe9ff1c8 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -1023,6 +1023,7 @@ after_listen:
 				tcpstat.tcps_rcvackbyte += acked;
 				sbdrop(&so->so_snd, acked);
 				tp->snd_una = th->th_ack;
+				tp->t_dupacks = 0;
 				m_freem(m);
 				ND6_HINT(tp); /* some progress has been done */