diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index 62508e786..b6d7939d2 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -67,9 +67,9 @@
 class HardwareSerial : public Stream
 {
   public:
-    virtual void begin(unsigned long);
-    virtual void begin(unsigned long baudrate, uint16_t config);
-    virtual void end();
+    virtual void begin(unsigned long) {}
+    virtual void begin(unsigned long baudrate, uint16_t config) {}
+    virtual void end() {}
     virtual int available(void) = 0;
     virtual int peek(void) = 0;
     virtual int read(void) = 0;