diff --git a/hardware/arduino/avr/cores/arduino/HardwareSerial_private.h b/hardware/arduino/avr/cores/arduino/HardwareSerial_private.h
index c0f631f80..d3e29c606 100644
--- a/hardware/arduino/avr/cores/arduino/HardwareSerial_private.h
+++ b/hardware/arduino/avr/cores/arduino/HardwareSerial_private.h
@@ -63,8 +63,8 @@ HardwareSerial::HardwareSerial(
     _ubrrh(ubrrh), _ubrrl(ubrrl),
     _ucsra(ucsra), _ucsrb(ucsrb), _ucsrc(ucsrc),
     _udr(udr),
-    _tx_buffer_head(0), _tx_buffer_tail(0),
-    _rx_buffer_head(0), _rx_buffer_tail(0)
+    _rx_buffer_head(0), _rx_buffer_tail(0),
+    _tx_buffer_head(0), _tx_buffer_tail(0)
 {
 }