diff --git a/SerialPort.cpp b/SerialPort.cpp
index f9bb4a2..e9c4fc1 100644
--- a/SerialPort.cpp
+++ b/SerialPort.cpp
@@ -72,7 +72,7 @@ m_len(0U)
 {
 }
 
-void CSerialPort::sendACK() const
+void CSerialPort::sendACK()
 {
   uint8_t reply[4U];
 
@@ -84,7 +84,7 @@ void CSerialPort::sendACK() const
   write(reply, 4);
 }
 
-void CSerialPort::sendNAK(uint8_t err) const
+void CSerialPort::sendNAK(uint8_t err)
 {
   uint8_t reply[5U];
 
@@ -97,7 +97,7 @@ void CSerialPort::sendNAK(uint8_t err) const
   write(reply, 5);
 }
 
-void CSerialPort::getStatus() const
+void CSerialPort::getStatus()
 {
   io.resetWatchdog();
 
@@ -153,7 +153,7 @@ void CSerialPort::getStatus() const
   write(reply, 10);
 }
 
-void CSerialPort::getVersion() const
+void CSerialPort::getVersion()
 {
   uint8_t reply[100U];
 
@@ -676,7 +676,7 @@ void CSerialPort::writeCalData(const uint8_t* data, uint8_t length)
   write(reply, count);
 }
 
-void CSerialPort::write(const uint8_t* data, uint16_t length, bool flush) const
+void CSerialPort::write(const uint8_t* data, uint16_t length, bool flush)
 {
 #if defined(__MBED__)
   for (uint16_t i = 0U; i < length; i++)
diff --git a/SerialPort.h b/SerialPort.h
index 850799a..0d8ce7c 100644
--- a/SerialPort.h
+++ b/SerialPort.h
@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -63,13 +63,13 @@ private:
   uint8_t m_ptr;
   uint8_t m_len;
 
-  void    sendACK() const;
-  void    sendNAK(uint8_t err) const;
-  void    getStatus() const;
-  void    getVersion() const;
+  void    sendACK();
+  void    sendNAK(uint8_t err);
+  void    getStatus();
+  void    getVersion();
   uint8_t setConfig(const uint8_t* data, uint8_t length);
   uint8_t setMode(const uint8_t* data, uint8_t length);
-  void    write(const uint8_t* data, uint16_t length, bool flush = false) const;
+  void    write(const uint8_t* data, uint16_t length, bool flush = false);
   void    setMode(MMDVM_STATE modemState);
 };