diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index 0a4d99ab40d8..fc6e709f45b1 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -371,6 +371,7 @@ __acquires(&port->port_lock)
 
 		req->length = len;
 		list_del(&req->list);
+		req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
 
 		pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
 				port->port_num, len, *((u8 *)req->buf),