diff --git a/hardware/arduino/avr/cores/arduino/PluggableUSB.cpp b/hardware/arduino/avr/cores/arduino/PluggableUSB.cpp
index 15195b01a..f59fc67e3 100644
--- a/hardware/arduino/avr/cores/arduino/PluggableUSB.cpp
+++ b/hardware/arduino/avr/cores/arduino/PluggableUSB.cpp
@@ -95,13 +95,13 @@ int8_t PUSB_AddFunction(PUSBCallbacks *cb, u8* interface)
 	}
 
 	*interface = lastIf;
-	lastIf++;
+	lastIf += cb->numInterfaces;
 	for ( u8 i = 0; i< cb->numEndpoints; i++) {
 		_initEndpoints[lastEp] = cb->endpointType[i];
 		lastEp++;
 	}
 	modules_count++;
-	return lastEp-1;
+	return lastEp - cb->numEndpoints;
 	// restart USB layer???
 }
 
diff --git a/hardware/arduino/avr/cores/arduino/PluggableUSB.h b/hardware/arduino/avr/cores/arduino/PluggableUSB.h
index e066d3775..8e7f5d761 100644
--- a/hardware/arduino/avr/cores/arduino/PluggableUSB.h
+++ b/hardware/arduino/avr/cores/arduino/PluggableUSB.h
@@ -31,6 +31,7 @@ typedef struct
   int8_t (*getInterface)(u8* interfaceNum);
   int8_t (*getDescriptor)(int8_t t);
   int8_t numEndpoints;
+  int8_t numInterfaces;
   u8 endpointType[];
 } PUSBCallbacks;
 
diff --git a/hardware/arduino/avr/cores/arduino/USBCore.cpp b/hardware/arduino/avr/cores/arduino/USBCore.cpp
index 53c71d905..d936a6bfb 100644
--- a/hardware/arduino/avr/cores/arduino/USBCore.cpp
+++ b/hardware/arduino/avr/cores/arduino/USBCore.cpp
@@ -33,7 +33,6 @@ extern const u16 STRING_LANGUAGE[] PROGMEM;
 extern const u8 STRING_PRODUCT[] PROGMEM;
 extern const u8 STRING_MANUFACTURER[] PROGMEM;
 extern const DeviceDescriptor USB_DeviceDescriptor PROGMEM;
-extern const DeviceDescriptor USB_DeviceDescriptorA PROGMEM;
 extern const DeviceDescriptor USB_DeviceDescriptorB PROGMEM;
 
 const u16 STRING_LANGUAGE[2] = {
@@ -72,9 +71,6 @@ const u8 STRING_MANUFACTURER[] PROGMEM = USB_MANUFACTURER;
 const DeviceDescriptor USB_DeviceDescriptor =
 	D_DEVICE(0x00,0x00,0x00,64,USB_VID,USB_PID,0x100,IMANUFACTURER,IPRODUCT,0,1);
 
-const DeviceDescriptor USB_DeviceDescriptorA =
-	D_DEVICE(DEVICE_CLASS,0x00,0x00,64,USB_VID,USB_PID,0x100,IMANUFACTURER,IPRODUCT,0,1);
-
 const DeviceDescriptor USB_DeviceDescriptorB =
 	D_DEVICE(0xEF,0x02,0x01,64,USB_VID,USB_PID,0x100,IMANUFACTURER,IPRODUCT,0,1);
 
diff --git a/libraries/HID/HID.cpp b/libraries/HID/HID.cpp
index e195f8e77..8bab60ae4 100644
--- a/libraries/HID/HID.cpp
+++ b/libraries/HID/HID.cpp
@@ -120,6 +120,7 @@ int8_t HID_Plug(void)
 	cb.getInterface = &HID_GetInterface;
 	cb.getDescriptor = &HID_GetDescriptor;
 	cb.numEndpoints = 1;
+	cb.numInterfaces = 1;
 	cb.endpointType[0] = EP_TYPE_INTERRUPT_IN;
 	HID_ENDPOINT_INT = PUSB_AddFunction(&cb, &HID_INTERFACE);
 
diff --git a/libraries/MIDIUSB/MIDIUSB.cpp b/libraries/MIDIUSB/MIDIUSB.cpp
index 329b40bc2..e3fab0e47 100644
--- a/libraries/MIDIUSB/MIDIUSB.cpp
+++ b/libraries/MIDIUSB/MIDIUSB.cpp
@@ -179,6 +179,7 @@ int8_t MIDI_plug(void)
 	cb.getInterface = &MIDI_GetInterface;
 	cb.getDescriptor = &MIDI_GetDescriptor;
 	cb.numEndpoints = 2;
+	cb.numInterfaces = 2;
 	cb.endpointType[0] = EP_TYPE_BULK_OUT_MIDI;		// MIDI_ENDPOINT_OUT
 	cb.endpointType[1] = EP_TYPE_BULK_IN_MIDI;		// MIDI_ENDPOINT_IN