diff --git a/drivers/serial/usbtty.c b/drivers/serial/usbtty.c
index 02f8edf200..4f4eb02de0 100644
--- a/drivers/serial/usbtty.c
+++ b/drivers/serial/usbtty.c
@@ -849,17 +849,9 @@ static int write_buffer (circbuf_t * buf)
 			&endpoint_instance[tx_endpoint];
 	struct urb *current_urb = NULL;
 
-	current_urb = next_urb (device_instance, endpoint);
-
-	if (!current_urb) {
-		TTYERR ("current_urb is NULL, buf->size %d\n",
-		buf->size);
-		return 0;
-	}
-
 	/* TX data still exists - send it now
 	 */
-	if(endpoint->sent < current_urb->actual_length){
+	if(endpoint->sent < endpoint->tx_urb->actual_length){
 		if(udc_endpoint_write (endpoint)){
 			/* Write pre-empted by RX */
 			return -1;
@@ -878,6 +870,8 @@ static int write_buffer (circbuf_t * buf)
 		 */
 		while (buf->size > 0) {
 
+			current_urb = next_urb (device_instance, endpoint);
+
 			dest = (char*)current_urb->buffer +
 				current_urb->actual_length;