diff --git a/src/ArduinoSTL.h b/src/ArduinoSTL.h
index 3fb432f8..b729f79b 100644
--- a/src/ArduinoSTL.h
+++ b/src/ArduinoSTL.h
@@ -9,6 +9,7 @@
 #ifndef ARDUINOSTL_M_H
 #define ARDUINOSTL_M_H
 
+#include "Arduino.h"
 #include <serstream>
 
 // Create cout and cin.. there doesn't seem to be a way