diff --git a/hardware/arduino/cores/arduino/CDC.cpp b/hardware/arduino/cores/arduino/CDC.cpp
index 701e48398..53f86f801 100644
--- a/hardware/arduino/cores/arduino/CDC.cpp
+++ b/hardware/arduino/cores/arduino/CDC.cpp
@@ -130,7 +130,7 @@ bool WEAK CDC_Setup(Setup& setup)
 
 
 int _serialPeek = -1;
-void Serial_::begin(uint16_t baud_count)
+void Serial_::begin(unsigned long baud_count)
 {
 }
 
diff --git a/hardware/arduino/cores/arduino/USBAPI.h b/hardware/arduino/cores/arduino/USBAPI.h
index eb2e5937d..d138a0efd 100644
--- a/hardware/arduino/cores/arduino/USBAPI.h
+++ b/hardware/arduino/cores/arduino/USBAPI.h
@@ -30,7 +30,7 @@ class Serial_ : public Stream
 private:
 	ring_buffer *_cdc_rx_buffer;
 public:
-	void begin(uint16_t baud_count);
+	void begin(unsigned long);
 	void end(void);
 
 	virtual int available(void);
@@ -193,4 +193,4 @@ void USB_Flush(uint8_t ep);
 
 #endif
 
-#endif /* if defined(USBCON) */
\ No newline at end of file
+#endif /* if defined(USBCON) */