diff --git a/cores/arduino/Print.cpp b/cores/arduino/Print.cpp
index e103ed6..8349c62 100644
--- a/cores/arduino/Print.cpp
+++ b/cores/arduino/Print.cpp
@@ -23,6 +23,9 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 #include "Print.h"
 #include "libcore/config/mcu_config.h"