diff --git a/cores/arduino/Serial.cpp b/cores/arduino/Serial.cpp
index 6b601907c..0a4239a45 100644
--- a/cores/arduino/Serial.cpp
+++ b/cores/arduino/Serial.cpp
@@ -38,6 +38,21 @@ struct _mbed_serial {
 	mbed::UnbufferedSerial* obj;
 };
 
+UART::UART(int tx, int rx, int rts, int cts) {
+	_tx = digitalPinToPinName(tx);
+	_rx = digitalPinToPinName(rx);
+	if (rts >= 0) {
+		_rts = digitalPinToPinName(rts);
+	} else {
+		_rts = NC;
+	}
+	if (cts >= 0) {
+		_cts = digitalPinToPinName(cts);
+	} else {
+		_cts = NC;
+	}
+}
+
 void UART::begin(unsigned long baudrate, uint16_t config) {
 
 #if defined(SERIAL_CDC)
diff --git a/cores/arduino/Serial.h b/cores/arduino/Serial.h
index 173c9663d..f20e14060 100644
--- a/cores/arduino/Serial.h
+++ b/cores/arduino/Serial.h
@@ -38,7 +38,8 @@ namespace arduino {
 
 class UART : public HardwareSerial {
 	public:
-		UART(int tx, int rx, int rts, int cts) : _tx((PinName)tx), _rx((PinName)rx), _rts((PinName)rts), _cts((PinName)cts) {}
+		UART(int tx, int rx, int rts = -1, int cts = -1);
+		UART(PinName tx, PinName rx, PinName rts = NC, PinName cts = NC) : _tx(tx), _rx(rx), _rts(rts), _cts(cts) {}
 		UART() {
 			is_usb = true;
 		}