diff --git a/core/common.hpp b/core/common.hpp
index 614dd4e..06e4fe1 100644
--- a/core/common.hpp
+++ b/core/common.hpp
@@ -44,6 +44,7 @@
 #include <iostream>
 #include <limits>
 #include <memory>
+#include <optional>
 #include <stdexcept>
 #include <string>
 #include <string_view>