diff --git a/include/utempl/utils.hpp b/include/utempl/utils.hpp
index 83dd9c7..ce0e8b2 100644
--- a/include/utempl/utils.hpp
+++ b/include/utempl/utils.hpp
@@ -2,7 +2,10 @@
 #include <utempl/tuple.hpp>
 #include <utempl/overloaded.hpp>
 #include <utempl/constexpr_string.hpp>
+#include <optional>
 #include <fmt/format.h>
+
+
 namespace utempl {
 
 template <auto Value>