diff --git a/source/mijin/container/optional.hpp b/source/mijin/container/optional.hpp
index 68fb75a..80f1fac 100644
--- a/source/mijin/container/optional.hpp
+++ b/source/mijin/container/optional.hpp
@@ -110,6 +110,8 @@ static constexpr NullOptional NULL_OPTIONAL;
 template<typename TValue>
 class Optional
 {
+public:
+    using value_t = TValue;
 private:
     impl::OptionalStorage<TValue> storage_ = {};
 public: