diff --git a/cores/arduino/PluggableUSB.cpp b/cores/arduino/PluggableUSB.cpp
index 15195b0..f59fc67 100644
--- a/cores/arduino/PluggableUSB.cpp
+++ b/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/cores/arduino/PluggableUSB.h b/cores/arduino/PluggableUSB.h
index e066d37..8e7f5d7 100644
--- a/cores/arduino/PluggableUSB.h
+++ b/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/cores/arduino/USBCore.cpp b/cores/arduino/USBCore.cpp
index 53c71d9..d936a6b 100644
--- a/cores/arduino/USBCore.cpp
+++ b/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);