diff --git a/src/game_api/online_util.hpp b/src/game_api/online_util.hpp
index 9bfea3f58..45b8d84ad 100644
--- a/src/game_api/online_util.hpp
+++ b/src/game_api/online_util.hpp
@@ -1,3 +1,4 @@
+#pragma once
 // Classes with only the functions that were currently used, more can be added if needed
 
 template <class T, class Allocator = std::allocator<T>>