diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 1b1d8fd634..57975975b9 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -116,7 +116,7 @@ HardwareSerial::HardwareSerial(PinName _rx, PinName _tx)
   init(_rx, _tx);
 }
 
-HardwareSerial::HardwareSerial(void *peripheral, bool halfDuplex)
+HardwareSerial::HardwareSerial(void *peripheral, HalfDuplexMode_t halfDuplex)
 {
   // If PIN_SERIALy_RX is not defined assume half-duplex
   _serial.pin_rx = NC;
@@ -247,7 +247,7 @@ HardwareSerial::HardwareSerial(void *peripheral, bool halfDuplex)
                           _serial.pin_rx = pinmap_pin(peripheral, PinMap_UART_RX);
                           _serial.pin_tx = pinmap_pin(peripheral, PinMap_UART_TX);
                         }
-  if (halfDuplex) {
+  if (halfDuplex == HALF_DUPLEX_ENABLED) {
     _serial.pin_rx = NC;
   }
   init(_serial.pin_rx, _serial.pin_tx);
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index a2a5644776..b9325858f5 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -57,6 +57,15 @@ typedef uint16_t rx_buffer_index_t;
 typedef uint8_t rx_buffer_index_t;
 #endif
 
+// A bool should be enough for this
+// But it brings an build error due to ambiguous
+// call of overloaded HardwareSerial(int, int)
+// So defining a dedicated type
+typedef enum {
+  HALF_DUPLEX_DISABLED,
+  HALF_DUPLEX_ENABLED
+} HalfDuplexMode_t;
+
 // Define config for Serial.begin(baud, config);
 // below configs are not supported by STM32
 //#define SERIAL_5N1 0x00
@@ -103,7 +112,7 @@ class HardwareSerial : public Stream {
   public:
     HardwareSerial(uint32_t _rx, uint32_t _tx);
     HardwareSerial(PinName _rx, PinName _tx);
-    HardwareSerial(void *peripheral, bool halfDuplex = false);
+    HardwareSerial(void *peripheral, HalfDuplexMode_t halfDuplex = HALF_DUPLEX_DISABLED);
     HardwareSerial(uint32_t _rxtx);
     HardwareSerial(PinName _rxtx);
     void begin(unsigned long baud)
diff --git a/keywords.txt b/keywords.txt
index 46f16f7a21..019b437912 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -270,6 +270,8 @@ PIN_WIRE_SCL	LITERAL1
 HardwareSerial	KEYWORD2
 setRx	KEYWORD2
 setTx	KEYWORD2
+HALF_DUPLEX_DISABLED	LITERAL1
+HALF_DUPLEX_ENABLED	LITERAL1
 setHalfDuplex	KEYWORD2
 isHalfDuplex	KEYWORD2
 enableHalfDuplexRx	KEYWORD2