diff --git a/server/src/hardware/protocol/dccplusplus/kernel.hpp b/server/src/hardware/protocol/dccplusplus/kernel.hpp
index 3256da2a..97583a34 100644
--- a/server/src/hardware/protocol/dccplusplus/kernel.hpp
+++ b/server/src/hardware/protocol/dccplusplus/kernel.hpp
@@ -25,6 +25,7 @@
 
 #include <array>
 #include <thread>
+#include <unordered_map>
 #include <boost/asio/io_context.hpp>
 #include <boost/asio/steady_timer.hpp>
 #include <traintastic/enum/tristate.hpp>