diff --git a/config.h b/config.h
index 0a8a4cd..918ecc9 100644
--- a/config.h
+++ b/config.h
@@ -17,6 +17,7 @@
 
 #pragma once
 
+#include <stddef.h>
 #include <stdint.h>
 #include <termios.h>