diff --git a/include/iris/alloy/tuple.hpp b/include/iris/alloy/tuple.hpp
index 55c60fd..14afe1f 100644
--- a/include/iris/alloy/tuple.hpp
+++ b/include/iris/alloy/tuple.hpp
@@ -269,6 +269,7 @@ class tuple : public detail::tuple_impl<Ts...>
 
     constexpr tuple& operator=(tuple const& other)
         noexcept(std::conjunction_v<std::is_nothrow_copy_assignable<Ts>...>)
+        requires std::conjunction_v<std::is_copy_assignable<Ts>...>
     {
         base_type::operator=(other);
         return *this;