diff --git a/single_include/flux.hpp b/single_include/flux.hpp
index 869731f8..09fcbca2 100644
--- a/single_include/flux.hpp
+++ b/single_include/flux.hpp
@@ -5321,8 +5321,9 @@ struct cartesian_power_fn {
 } // end namespace detail
 
 FLUX_EXPORT
-template<std::size_t PowN>
-inline constexpr auto cartesian_power = detail::cartesian_power_fn<PowN>{};
+template<distance_t N>
+    requires (N >= 0)
+inline constexpr auto cartesian_power = detail::cartesian_power_fn<N>{};
 
 } // end namespace flux