diff --git a/src/common/bitsery/ext/message-reference.h b/src/common/bitsery/ext/message-reference.h
index e2da77a0..cf43ebe1 100644
--- a/src/common/bitsery/ext/message-reference.h
+++ b/src/common/bitsery/ext/message-reference.h
@@ -17,6 +17,8 @@
 
 #pragma once
 
+#include <optional>
+
 #include <bitsery/details/serialization_common.h>
 #include <bitsery/traits/core/traits.h>