diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 11ec7d2d74d..15b7311f460 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -3972,7 +3972,7 @@ tcp_do_prr_ack(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
 			    imax(1, tp->snd_nxt - tp->snd_una);
 		snd_cnt = howmany((long)tp->sackhint.prr_delivered *
 			    tp->snd_ssthresh, tp->sackhint.recover_fs) -
-			    tp->sackhint.prr_out;
+			    tp->sackhint.prr_out + maxseg - 1;
 	} else {
 		if (V_tcp_do_prr_conservative || (del_data == 0))
 			limit = tp->sackhint.prr_delivered -