diff --git a/hardware/arduino/avr/variants/ethernet/pins_arduino.h b/hardware/arduino/avr/variants/ethernet/pins_arduino.h
index 77fcc40cc67..f12f3215bf6 100644
--- a/hardware/arduino/avr/variants/ethernet/pins_arduino.h
+++ b/hardware/arduino/avr/variants/ethernet/pins_arduino.h
@@ -250,5 +250,6 @@ const uint8_t PROGMEM digital_pin_to_timer_PGM[] = {
 //                            pins are NOT connected to anything by default.
 #define SERIAL_PORT_HARDWARE       Serial
 #define SERIAL_PORT_HARDWARE_OPEN  Serial
+#define SERIAL_PORT_MONITOR        Serial
 
 #endif