diff --git a/serial_win32.c b/serial_win32.c
index bfb4f9d..b951708 100644
--- a/serial_win32.c
+++ b/serial_win32.c
@@ -1,4 +1,4 @@
-#include <stddef.h>
+#include <stdlib.h>
 #include <windows.h>
 
 #include "serial.h"