diff --git a/drivers/usb/serial/usb_debug.c b/drivers/usb/serial/usb_debug.c
index fc5d995..6c9cbb5 100644
--- a/drivers/usb/serial/usb_debug.c
+++ b/drivers/usb/serial/usb_debug.c
@@ -31,7 +31,7 @@
 	.no_dynamic_id = 	1,
 };
 
-int usb_debug_open(struct tty_struct *tty, struct usb_serial_port *port,
+static int usb_debug_open(struct tty_struct *tty, struct usb_serial_port *port,
 							struct file *filp)
 {
 	port->bulk_out_size = USB_DEBUG_MAX_PACKET_SIZE;