From 5f73123f8756ebcd5badaa8dae3252f595a1c82f Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Mon, 9 Mar 2020 18:56:55 +0100
Subject: [PATCH] Contrained on a named unit added to a `prefixed_unit`

---
 src/include/units/unit.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/include/units/unit.h b/src/include/units/unit.h
index c9c43e4f..9471f993 100644
--- a/src/include/units/unit.h
+++ b/src/include/units/unit.h
@@ -134,7 +134,7 @@ struct named_scaled_unit : downcast_child<Child, scaled_unit<ratio_multiply<R, t
  * @tparam U reference unit
  */
 template<typename Child, Prefix P, Unit U>
-  requires std::same_as<typename P::prefix_type, typename U::prefix_type>
+  requires U::is_named && std::same_as<typename P::prefix_type, typename U::prefix_type>
 struct prefixed_unit :
     downcast_child<Child, scaled_unit<ratio_multiply<typename P::ratio, typename U::ratio>, typename U::reference>> {
   static constexpr bool is_named = true;