diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1649,6 +1649,7 @@
 		if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
 			to.to_tsecr = 0;
 		else if (tp->t_flags & TF_PREVVALID &&
+			 tp->t_rxtshift == 1 &&
 			 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin))
 			cc_cong_signal(tp, th, CC_RTO_ERR);
 	}
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -506,7 +506,11 @@
 #define	TF_NEEDSYN	0x00000400	/* send SYN (implicit state) */
 #define	TF_NEEDFIN	0x00000800	/* send FIN (implicit state) */
 #define	TF_NOPUSH	0x00001000	/* don't push */
-#define	TF_PREVVALID	0x00002000	/* saved values for bad rxmit valid */
+#define	TF_PREVVALID	0x00002000	/* saved values for bad rxmit valid
+					 * Note: accessing and restoring from
+					 * these may only be done in the 1st
+					 * RTO recovery round (t_rxtshift == 1)
+					 */
 #define	TF_WAKESOR	0x00004000	/* wake up receive socket */
 #define	TF_GPUTINPROG	0x00008000	/* Goodput measurement in progress */
 #define	TF_MORETOCOME	0x00010000	/* More data to be appended to sock */