diff --git a/hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.h b/hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.h
index 27c0bfca9..778fffbf5 100644
--- a/hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.h
+++ b/hardware/arduino/avr/libraries/SoftwareSerial/SoftwareSerial.h
@@ -71,7 +71,7 @@ private:
   // private methods
   void recv();
   uint8_t rx_pin_read();
-  void tx_pin_write(uint8_t pin_state);
+  void tx_pin_write(uint8_t pin_state) __attribute__((__always_inline__));
   void setTX(uint8_t transmitPin);
   void setRX(uint8_t receivePin);
   void setRxIntMsk(bool enable);