diff --git a/src/core/include/units/quantity_cast.h b/src/core/include/units/quantity_cast.h
index 5295f3a1..61678558 100644
--- a/src/core/include/units/quantity_cast.h
+++ b/src/core/include/units/quantity_cast.h
@@ -53,9 +53,6 @@ namespace detail {
 template<Quantity Q>
 inline constexpr Magnitude auto quantity_magnitude = decltype(Q::reference)::mag;
 
-template<Quantity Q>
-inline constexpr ratio quantity_ratio = as_ratio(quantity_magnitude<Q>);
-
 template<typename QFrom, typename QTo>
 inline constexpr Magnitude auto cast_magnitude = [] {
   using FromU = TYPENAME QFrom::unit;
diff --git a/test/unit_test/static/si_cgs_test.cpp b/test/unit_test/static/si_cgs_test.cpp
index 8c817f08..d502cffe 100644
--- a/test/unit_test/static/si_cgs_test.cpp
+++ b/test/unit_test/static/si_cgs_test.cpp
@@ -36,13 +36,16 @@ namespace {
 
 using namespace units::isq;
 
-static_assert(units::detail::quantity_ratio<si::length<si::metre>> == units::ratio(1));
-static_assert(units::detail::quantity_ratio<si::cgs::length<si::cgs::centimetre>> == units::ratio(1, 100));
-static_assert(units::detail::quantity_ratio<si::speed<si::metre_per_second>> == units::ratio(1));
-static_assert(units::detail::quantity_ratio<si::cgs::speed<si::cgs::centimetre_per_second>> == units::ratio(1, 100));
-static_assert(units::detail::quantity_ratio<si::force<si::newton>> ==
+template<units::Quantity Q>
+inline constexpr units::ratio quantity_ratio = units::as_ratio(units::detail::quantity_magnitude<Q>);
+
+static_assert(quantity_ratio<si::length<si::metre>> == units::ratio(1));
+static_assert(quantity_ratio<si::cgs::length<si::cgs::centimetre>> == units::ratio(1, 100));
+static_assert(quantity_ratio<si::speed<si::metre_per_second>> == units::ratio(1));
+static_assert(quantity_ratio<si::cgs::speed<si::cgs::centimetre_per_second>> == units::ratio(1, 100));
+static_assert(quantity_ratio<si::force<si::newton>> ==
               units::ratio(1000));  // defined in terms of kilogram that are 1000 * gram
-static_assert(units::detail::quantity_ratio<si::cgs::force<si::cgs::dyne>> ==
+static_assert(quantity_ratio<si::cgs::force<si::cgs::dyne>> ==
               units::ratio(1, 100));  // defined in terms of gram so only centimetre ratio counts here
 
 static_assert(si::cgs::length<si::cgs::centimetre>(100) == si::length<si::metre>(1));
diff --git a/test/unit_test/static/si_hep_test.cpp b/test/unit_test/static/si_hep_test.cpp
index 87045e63..62479696 100644
--- a/test/unit_test/static/si_hep_test.cpp
+++ b/test/unit_test/static/si_hep_test.cpp
@@ -31,7 +31,10 @@ namespace {
 
 using namespace units::isq;
 
-static_assert(units::detail::quantity_ratio<si::length<si::metre>> == units::ratio(1));
+template<units::Quantity Q>
+inline constexpr units::ratio quantity_ratio = units::as_ratio(units::detail::quantity_magnitude<Q>);
+
+static_assert(quantity_ratio<si::length<si::metre>> == units::ratio(1));
 
 // mass
 static_assert(si::hep::mass<si::hep::eV_per_c2>(1'000) == si::hep::mass<si::hep::keV_per_c2>(1));