diff --git a/hardware/arduino/avr/cores/arduino/CDC.cpp b/hardware/arduino/avr/cores/arduino/CDC.cpp
index fb25a9622..a69130660 100644
--- a/hardware/arduino/avr/cores/arduino/CDC.cpp
+++ b/hardware/arduino/avr/cores/arduino/CDC.cpp
@@ -115,7 +115,11 @@ bool WEAK CDC_Setup(Setup& setup)
 
 
 int _serialPeek = -1;
-void Serial_::begin(uint16_t baud_count)
+void Serial_::begin(unsigned long baud_count)
+{
+}
+
+void Serial_::begin(unsigned long baud_count, byte config)
 {
 }
 
diff --git a/hardware/arduino/avr/cores/arduino/USBAPI.h b/hardware/arduino/avr/cores/arduino/USBAPI.h
index cabecf354..da2e86961 100644
--- a/hardware/arduino/avr/cores/arduino/USBAPI.h
+++ b/hardware/arduino/avr/cores/arduino/USBAPI.h
@@ -36,7 +36,8 @@ struct ring_buffer;
 class Serial_ : public Stream
 {
 public:
-	void begin(uint16_t baud_count);
+	void begin(unsigned long);
+	void begin(unsigned long, uint8_t);
 	void end(void);
 
 	virtual int available(void);