diff --git a/include/linux/usb/serial.h b/include/linux/usb/serial.h
index b9b0f7b4..afbb7ee 100644
--- a/include/linux/usb/serial.h
+++ b/include/linux/usb/serial.h
@@ -268,6 +268,7 @@
 			struct usb_serial_port *port, struct ktermios *old);
 	void (*break_ctl)(struct tty_struct *tty, int break_state);
 	int  (*chars_in_buffer)(struct tty_struct *tty);
+	void (*wait_until_sent)(struct tty_struct *tty, long timeout);
 	void (*throttle)(struct tty_struct *tty);
 	void (*unthrottle)(struct tty_struct *tty);
 	int  (*tiocmget)(struct tty_struct *tty);