diff --git a/hash/tuple.hpp b/hash/tuple.hpp
index 8e7c47d5..f36961e3 100644
--- a/hash/tuple.hpp
+++ b/hash/tuple.hpp
@@ -17,6 +17,8 @@ namespace cruft::hash {
     >
     class tuple {
     public:
+        using is_transparent = void;
+
         template <typename ...ValueT>
         auto
         operator() (std::tuple<ValueT...> const &val) const