diff --git a/include/boost/unordered/detail/opt_storage.hpp b/include/boost/unordered/detail/opt_storage.hpp
index e18c2ce8..c38b5879 100644
--- a/include/boost/unordered/detail/opt_storage.hpp
+++ b/include/boost/unordered/detail/opt_storage.hpp
@@ -1,3 +1,8 @@
+// Copyright (C) 2023 Christian Mazakas
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
 #ifndef BOOST_UNORDERED_DETAIL_OPT_STORAGE_HPP
 #define BOOST_UNORDERED_DETAIL_OPT_STORAGE_HPP
 
@@ -22,4 +27,4 @@ namespace boost {
   } // namespace unordered
 } // namespace boost
 
-#endif // BOOST_UNORDERED_DETAIL_OPT_STORAGE_HPP
\ No newline at end of file
+#endif // BOOST_UNORDERED_DETAIL_OPT_STORAGE_HPP