diff --git a/src/include/units/bits/ratio_tools.h b/src/include/units/bits/ratio_tools.h
index 2e8bcb90..4c906e7c 100644
--- a/src/include/units/bits/ratio_tools.h
+++ b/src/include/units/bits/ratio_tools.h
@@ -69,16 +69,19 @@ namespace units {
   concept bool Ratio = detail::is_ratio<T>;
 
   // common_ratio
+  namespace detail {
 
-  // todo: simplified
-  template<Ratio R1, Ratio R2>
-  struct common_ratio {
-    using gcd_num = static_gcd<R1::num, R2::num>;
-    using gcd_den = static_gcd<R1::den, R2::den>;
-    using type = std::ratio<gcd_num::value, (R1::den / gcd_den::value) * R2::den>;
-  };
+    // todo: simplified
+    template<typename R1, typename R2>
+    struct common_ratio_impl {
+      using gcd_num = static_gcd<R1::num, R2::num>;
+      using gcd_den = static_gcd<R1::den, R2::den>;
+      using type = std::ratio<gcd_num::value, (R1::den / gcd_den::value) * R2::den>;
+    };
+
+  }
 
   template<Ratio R1, Ratio R2>
-  using common_ratio_t = common_ratio<R1, R2>::type;
+  using common_ratio = detail::common_ratio_impl<R1, R2>::type;
 
 }  // namespace units
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 82029294..e91d65dd 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -67,7 +67,7 @@ namespace units {
 
   template<Dimension D, Unit U1, Scalar Rep1, Unit U2, Scalar Rep2, Scalar Rep>
   struct common_quantity<quantity<D, U1, Rep1>, quantity<D, U2, Rep2>, Rep> {
-    using type = quantity<D, upcasting_traits_t<unit<D, common_ratio_t<typename U1::ratio, typename U2::ratio>>>, Rep>;
+    using type = quantity<D, upcasting_traits_t<unit<D, common_ratio<typename U1::ratio, typename U2::ratio>>>, Rep>;
   };
 
   template<Quantity Q1, Quantity Q2, Scalar Rep = std::common_type_t<typename Q1::rep, typename Q2::rep>>
diff --git a/test/unit_test/test_tools.cpp b/test/unit_test/test_tools.cpp
index d65b0270..1f3fec6c 100644
--- a/test/unit_test/test_tools.cpp
+++ b/test/unit_test/test_tools.cpp
@@ -40,9 +40,9 @@ namespace {
 
   // common_ratio
 
-  static_assert(std::is_same_v<common_ratio_t<std::ratio<1>, std::kilo>, std::ratio<1>>);
-  static_assert(std::is_same_v<common_ratio_t<std::kilo, std::ratio<1>>, std::ratio<1>>);
-  static_assert(std::is_same_v<common_ratio_t<std::ratio<1>, std::milli>, std::milli>);
-  static_assert(std::is_same_v<common_ratio_t<std::milli, std::ratio<1>>, std::milli>);
+  static_assert(std::is_same_v<common_ratio<std::ratio<1>, std::kilo>, std::ratio<1>>);
+  static_assert(std::is_same_v<common_ratio<std::kilo, std::ratio<1>>, std::ratio<1>>);
+  static_assert(std::is_same_v<common_ratio<std::ratio<1>, std::milli>, std::milli>);
+  static_assert(std::is_same_v<common_ratio<std::milli, std::ratio<1>>, std::milli>);
 
 }  // namespace
\ No newline at end of file