diff --git a/usb/v1_0/UsbTypes.idl b/usb/v1_0/UsbTypes.idl
index 055480eb15d5815a7fb2a98e8f68cd4875a676d2..2786d17472f61233b3672dc48b14c0acbdd9e961 100644
--- a/usb/v1_0/UsbTypes.idl
+++ b/usb/v1_0/UsbTypes.idl
@@ -61,6 +61,7 @@ struct UsbCtrlTransfer {
     int requestCmd;
     int value;
     int index;
+    int length;
     int timeout;
 };