diff --git a/hw/usb.h b/hw/usb.h
index 9cd2f896661986ba2c5f04e2b88cda0e769cb941..7ed8fb8fcf2dc6d94f3331dc988e6d21e267a17b 100644
--- a/hw/usb.h
+++ b/hw/usb.h
@@ -145,6 +145,8 @@
 #define USB_ENDPOINT_XFER_INT		3
 #define USB_ENDPOINT_XFER_INVALID     255
 
+#define USB_INTERFACE_INVALID         255
+
 typedef struct USBBus USBBus;
 typedef struct USBBusOps USBBusOps;
 typedef struct USBPort USBPort;
diff --git a/hw/usb/core.c b/hw/usb/core.c
index fe15be064f4a8c353c2be90028ce0e9a7cd04b63..0614f76f4f1812887a810ce052613c873248c3eb 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -566,8 +566,8 @@ void usb_ep_reset(USBDevice *dev)
         dev->ep_out[ep].pid = USB_TOKEN_OUT;
         dev->ep_in[ep].type = USB_ENDPOINT_XFER_INVALID;
         dev->ep_out[ep].type = USB_ENDPOINT_XFER_INVALID;
-        dev->ep_in[ep].ifnum = 0;
-        dev->ep_out[ep].ifnum = 0;
+        dev->ep_in[ep].ifnum = USB_INTERFACE_INVALID;
+        dev->ep_out[ep].ifnum = USB_INTERFACE_INVALID;
         dev->ep_in[ep].dev = dev;
         dev->ep_out[ep].dev = dev;
         dev->ep_in[ep].pipeline = false;