diff --git a/drivers/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c
index a62981ca7a73..f93b81a297d6 100644
--- a/drivers/usb/serial/quatech2.c
+++ b/drivers/usb/serial/quatech2.c
@@ -841,7 +841,10 @@ static void qt2_update_msr(struct usb_serial_port *port, unsigned char *ch)
 	u8 newMSR = (u8) *ch;
 	unsigned long flags;
 
+	/* May be called from qt2_process_read_urb() for an unbound port. */
 	port_priv = usb_get_serial_port_data(port);
+	if (!port_priv)
+		return;
 
 	spin_lock_irqsave(&port_priv->lock, flags);
 	port_priv->shadowMSR = newMSR;
@@ -869,7 +872,10 @@ static void qt2_update_lsr(struct usb_serial_port *port, unsigned char *ch)
 	unsigned long flags;
 	u8 newLSR = (u8) *ch;
 
+	/* May be called from qt2_process_read_urb() for an unbound port. */
 	port_priv = usb_get_serial_port_data(port);
+	if (!port_priv)
+		return;
 
 	if (newLSR & UART_LSR_BI)
 		newLSR &= (u8) (UART_LSR_OE | UART_LSR_BI);