diff --git a/command/rakp12.hpp b/command/rakp12.hpp
index b615c7b..c19853f 100644
--- a/command/rakp12.hpp
+++ b/command/rakp12.hpp
@@ -3,6 +3,7 @@
 #include "comm_module.hpp"
 #include "message_handler.hpp"
 
+#include <cstddef>
 #include <vector>
 
 namespace command