diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 1dc6af2ca3e4..e28b303cefa9 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -213,7 +213,7 @@ ttydev_leave(struct tty *tp)
 
 	ttydisc_close(tp);
 
-	/* Destroy associated buffers already. */
+	/* Free i/o queues now since they might be large. */
 	ttyinq_free(&tp->t_inq);
 	tp->t_inlow = 0;
 	ttyoutq_free(&tp->t_outq);
@@ -1031,10 +1031,15 @@ tty_dealloc(void *arg)
 {
 	struct tty *tp = arg;
 
-	/* Make sure we haven't leaked buffers. */
-	MPASS(ttyinq_getsize(&tp->t_inq) == 0);
-	MPASS(ttyoutq_getsize(&tp->t_outq) == 0);
-
+	/*
+	 * ttyydev_leave() usually frees the i/o queues earlier, but it is
+	 * not always called between queue allocation and here.  The queues
+	 * may be allocated by ioctls on a pty control device without the
+	 * corresponding pty slave device ever being open, or after it is
+	 * closed.
+	 */
+	ttyinq_free(&tp->t_inq);
+	ttyoutq_free(&tp->t_outq);
 	seldrain(&tp->t_inpoll);
 	seldrain(&tp->t_outpoll);
 	knlist_destroy(&tp->t_inpoll.si_note);