diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index 244acb1299a9..e92cd1eceefa 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -773,7 +773,7 @@ send:
 
 	usb_fill_int_urb(port->interrupt_out_urb, port->serial->dev,
 		usb_sndintpipe(port->serial->dev, port->interrupt_out_endpointAddress),
-		port->interrupt_out_buffer, port->interrupt_out_size,
+		port->interrupt_out_buffer, actual_size,
 		cypress_write_int_callback, port, priv->write_urb_interval);
 	result = usb_submit_urb(port->interrupt_out_urb, GFP_ATOMIC);
 	if (result) {