diff --git a/include/linux/tty.h b/include/linux/tty.h
index 1b76106..59ff42c 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -345,6 +345,7 @@
 extern void stop_tty(struct tty_struct * tty);
 extern void start_tty(struct tty_struct * tty);
 extern int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc);
+extern int tty_unregister_ldisc(int disc);
 extern int tty_register_driver(struct tty_driver *driver);
 extern int tty_unregister_driver(struct tty_driver *driver);
 extern void tty_register_device(struct tty_driver *driver, unsigned index, struct device *dev);