diff --git a/include/json_html_serializer.hpp b/include/json_html_serializer.hpp
index ede2c89..a4bcdcb 100644
--- a/include/json_html_serializer.hpp
+++ b/include/json_html_serializer.hpp
@@ -1,3 +1,5 @@
+#pragma once
+
 #include "http_response.hpp"
 
 #include <nlohmann/json.hpp>