diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index d4b14c30794e2ec78c6f83c57376a17f4e4fdda7..7efabc4673b6a79d8822264a02a4c8afd09a91d8 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -262,7 +262,7 @@ static void n_tty_check_throttle(struct tty_struct *tty)
 	while (1) {
 		int throttled;
 		tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
-		if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
+		if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
 			break;
 		throttled = tty_throttle_safe(tty);
 		if (!throttled)