diff --git a/usb/endpoint.go b/usb/endpoint.go
index 68fbcdf..52bff35 100644
--- a/usb/endpoint.go
+++ b/usb/endpoint.go
@@ -74,7 +74,7 @@ func (e *endpoint) transfer(buf []byte, timeout time.Duration) (int, error) {
 		return 0, err
 	}
 
-	n, err := t.wait(buf)
+	n, err := t.wait()
 	if err != nil {
 		log.Printf("bulk: %s failed: %s", tt, err)
 		return 0, err
diff --git a/usb/transfer.go b/usb/transfer.go
index 4018ba2..0e22080 100644
--- a/usb/transfer.go
+++ b/usb/transfer.go
@@ -50,7 +50,7 @@ func (t *usbTransfer) submit(timeout time.Duration) error {
 	return nil
 }
 
-func (t *usbTransfer) wait(b []byte) (n int, err error) {
+func (t *usbTransfer) wait() (n int, err error) {
 	select {
 	case <-time.After(10 * time.Second):
 		return 0, fmt.Errorf("wait timed out after 10s")
@@ -59,9 +59,9 @@ func (t *usbTransfer) wait(b []byte) (n int, err error) {
 	var status uint8
 	switch TransferType(t.xfer._type) {
 	case TRANSFER_TYPE_ISOCHRONOUS:
-		n = int(C.extract_iso_data(t.xfer, unsafe.Pointer(&b[0]), C.int(len(b)), (*C.uchar)(unsafe.Pointer(&status))))
+		n = int(C.extract_iso_data(t.xfer, unsafe.Pointer(&t.buf[0]), C.int(len(t.buf)), (*C.uchar)(unsafe.Pointer(&status))))
 	default:
-		n = int(C.extract_data(t.xfer, unsafe.Pointer(&b[0]), C.int(len(b)), (*C.uchar)(unsafe.Pointer(&status))))
+		n = int(C.extract_data(t.xfer, unsafe.Pointer(&t.buf[0]), C.int(len(t.buf)), (*C.uchar)(unsafe.Pointer(&status))))
 	}
 	if status != 0 {
 		err = TransferStatus(status)