diff --git a/simulator/httpd/reply.hpp b/simulator/httpd/reply.hpp
index 4c3cd74..1aeb428 100644
--- a/simulator/httpd/reply.hpp
+++ b/simulator/httpd/reply.hpp
@@ -11,6 +11,7 @@
 #ifndef HTTP_REPLY_HPP
 #define HTTP_REPLY_HPP
 
+#include <map>
 #include <string>
 #include <vector>
 #include <boost/asio.hpp>