Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -2374,12 +2374,6 @@
 		if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
 			tcp_fastopen_decrement_counter(tp->t_tfo_pending);
 			tp->t_tfo_pending = NULL;
-
-			/*
-			 * Account for the ACK of our SYN prior to
-			 * regular ACK processing below.
-			 */
-			tp->snd_una++;
 		}
 		if (tp->t_flags & TF_NEEDFIN) {
 			tcp_state_change(tp, TCPS_FIN_WAIT_1);
@@ -2399,6 +2393,12 @@
 				cc_conn_init(tp);
 			tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
 		}
+		if (SEQ_GT(th->th_ack, tp->snd_una))
+			/*
+			 * Account for the ACK of our SYN prior to
+			 * regular ACK processing below.
+			 */
+			tp->snd_una++;
 		/*
 		 * If segment contains data or ACK, will call tcp_reass()
 		 * later; if not, do so now to pass queued data to user.
Index: sys/netinet/tcp_stacks/bbr.c
===================================================================
--- sys/netinet/tcp_stacks/bbr.c
+++ sys/netinet/tcp_stacks/bbr.c
@@ -9325,11 +9325,6 @@
 
 		tcp_fastopen_decrement_counter(tp->t_tfo_pending);
 		tp->t_tfo_pending = NULL;
-		/*
-		 * Account for the ACK of our SYN prior to regular
-		 * ACK processing below.
-		 */
-		tp->snd_una++;
 	}
 	/*
 	 * Make transitions: SYN-RECEIVED  -> ESTABLISHED SYN-RECEIVED* ->
@@ -9352,6 +9347,12 @@
 		if (!IS_FASTOPEN(tp->t_flags))
 			cc_conn_init(tp);
 	}
+	if (SEQ_GT(th->th_ack, tp->snd_una))
+		/*
+		 * Account for the ACK of our SYN prior to
+		 * regular ACK processing below.
+		 */
+		tp->snd_una++;
 	/*
 	 * If segment contains data or ACK, will call tcp_reass() later; if
 	 * not, do so now to pass queued data to user.
Index: sys/netinet/tcp_stacks/rack.c
===================================================================
--- sys/netinet/tcp_stacks/rack.c
+++ sys/netinet/tcp_stacks/rack.c
@@ -6539,12 +6539,6 @@
 	if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
 		tcp_fastopen_decrement_counter(tp->t_tfo_pending);
 		tp->t_tfo_pending = NULL;
-
-		/*
-		 * Account for the ACK of our SYN prior to
-		 * regular ACK processing below.
-		 */
-		tp->snd_una++;
 	}
 	if (tp->t_flags & TF_NEEDFIN) {
 		tcp_state_change(tp, TCPS_FIN_WAIT_1);
@@ -6562,6 +6556,12 @@
 		if (!IS_FASTOPEN(tp->t_flags))
 			cc_conn_init(tp);
 	}
+	if (SEQ_GT(th->th_ack, tp->snd_una))
+		/*
+		 * Account for the ACK of our SYN prior to
+		 * regular ACK processing below.
+		 */
+		tp->snd_una++;
 	/*
 	 * If segment contains data or ACK, will call tcp_reass() later; if
 	 * not, do so now to pass queued data to user.