diff --git a/src/core/include/mp-units/framework/reference.h b/src/core/include/mp-units/framework/reference.h
index ee9f1ad2..d4af7fba 100644
--- a/src/core/include/mp-units/framework/reference.h
+++ b/src/core/include/mp-units/framework/reference.h
@@ -287,10 +287,8 @@ constexpr auto operator/(R, Q&& q) = delete;
 [[nodiscard]] consteval AssociatedUnit auto get_common_reference(AssociatedUnit auto u1, AssociatedUnit auto u2,
                                                                  AssociatedUnit auto... rest)
   requires requires {
-    {
-      get_common_quantity_spec(get_quantity_spec(u1), get_quantity_spec(u2), get_quantity_spec(rest)...)
-    } -> QuantitySpec;
-    { get_common_unit(u1, u2, rest...) } -> AssociatedUnit;
+    get_common_quantity_spec(get_quantity_spec(u1), get_quantity_spec(u2), get_quantity_spec(rest)...);
+    get_common_unit(u1, u2, rest...);
   }
 {
   return get_common_unit(u1, u2, rest...);
@@ -299,10 +297,8 @@ constexpr auto operator/(R, Q&& q) = delete;
 template<Reference R1, Reference R2, Reference... Rest>
 [[nodiscard]] consteval Reference auto get_common_reference(R1 r1, R2 r2, Rest... rest)
   requires(!(AssociatedUnit<R1> && AssociatedUnit<R2> && (... && AssociatedUnit<Rest>))) && requires {
-    {
-      get_common_quantity_spec(get_quantity_spec(r1), get_quantity_spec(r2), get_quantity_spec(rest)...)
-    } -> QuantitySpec;
-    { get_common_unit(get_unit(r1), get_unit(r2), get_unit(rest)...) } -> Unit;
+    get_common_quantity_spec(get_quantity_spec(r1), get_quantity_spec(r2), get_quantity_spec(rest)...);
+    get_common_unit(get_unit(r1), get_unit(r2), get_unit(rest)...);
   }
 {
   return detail::reference_t<get_common_quantity_spec(get_quantity_spec(R1{}), get_quantity_spec(R2{}),