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
@@ -3600,7 +3600,8 @@
 	INP_WLOCK_ASSERT(tptoinpcb(tp));
 
 	TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UTYPE_MAX(tp->t_rttupdated))
+		tp->t_rttupdated++;
 #ifdef STATS
 	stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT,
 	    imax(0, rtt * 1000 / hz));
diff --git a/sys/netinet/tcp_stacks/bbr.c b/sys/netinet/tcp_stacks/bbr.c
--- a/sys/netinet/tcp_stacks/bbr.c
+++ b/sys/netinet/tcp_stacks/bbr.c
@@ -6397,7 +6397,8 @@
 		tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
 	}
 	KMOD_TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UTYPE_MAX(tp->t_rttupdated))
+		tp->t_rttupdated++;
 #ifdef STATS
 	stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, imax(0, rtt_ticks));
 #endif
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -7725,7 +7725,8 @@
 	}
 	rack->rc_srtt_measure_made = 1;
 	KMOD_TCPSTAT_INC(tcps_rttupdated);
-	tp->t_rttupdated++;
+	if (tp->t_rttupdated < UTYPE_MAX(tp->t_rttupdated))
+		tp->t_rttupdated++;
 #ifdef STATS
 	if (rack_stats_gets_ms_rtt == 0) {
 		/* Send in the microsecond rtt used for rxt timeout purposes */
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -3136,7 +3136,7 @@
 	    tp->t_rttbest);
 
 	db_print_indent(indent);
-	db_printf("t_rttupdated: %lu   max_sndwnd: %u   t_softerror: %d\n",
+	db_printf("t_rttupdated: %u   max_sndwnd: %u   t_softerror: %d\n",
 	    tp->t_rttupdated, tp->max_sndwnd, tp->t_softerror);
 
 	db_print_indent(indent);
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
@@ -222,7 +222,6 @@
 	uint32_t snd_ssthresh_prev;	/* ssthresh prior to retransmit */
 	tcp_seq	snd_recover_prev;	/* snd_recover prior to retransmit */
 	int	t_sndzerowin;		/* zero-window updates sent */
-	u_long	t_rttupdated;		/* number of times rtt sampled */
 	int	snd_numholes;		/* number of holes seen by sender */
 	u_int	t_badrxtwin;		/* window for retransmit recovery */
 	TAILQ_HEAD(sackhole_head, sackhole) snd_holes;
@@ -269,6 +268,7 @@
 	uint32_t t_dsack_bytes;		/* dsack bytes received */
 	uint32_t t_dsack_tlp_bytes;	/* dsack bytes received for TLPs sent */
 	uint32_t t_dsack_pack;		/* dsack packets we have eceived */
+	uint8_t t_rttupdated;		/* number of times rtt sampled */
 	/* TCP Fast Open */
 	uint8_t t_tfo_client_cookie_len; /* TFO client cookie length */
 	uint32_t t_end_info_status;	/* Status flag of end info */
@@ -682,6 +682,22 @@
 	max((tp)->t_rttmin, (((tp)->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT))  \
 	  + (tp)->t_rttvar) >> TCP_DELTA_SHIFT)
 
+/*
+ * Programmatically determine the maximum value of
+ * an unsigned type, without integer overflow.
+ *
+ * After determining the byte-size of the type,
+ * e.g. 2 for uint16, set the left-most bit. (0x8000)
+ * Set all bits but the highest by subtracting one. (0x7FFF)
+ * Shift all set bits left by one by way of muliply by 2. (0xFFFE)
+ * Finally, set the lowest bit by adding one. (0xFFFF)
+ *
+ * This is a portable way to programmatically determine
+ * the maximum value of an unsigned variable of arbitrary size.
+ */
+#define UTYPE_MAX(x) \
+	((((1ULL << (sizeof((x)) * 8 - 1)) - 1) * 2) + 1)
+
 /*
  * TCP statistics.
  * Many of these should be kept per connection,