diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index bdb8fd1..11db7dc 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -399,6 +399,8 @@
 	if (!o_tty)
 		goto err_put_module;
 
+	tty_set_lock_subclass(o_tty);
+
 	if (legacy) {
 		/* We always use new tty termios data so we can do this
 		   the easy way .. */