diff --git a/parallel_hashmap/btree.h b/parallel_hashmap/btree.h
index 322f028..a9fcb93 100644
--- a/parallel_hashmap/btree.h
+++ b/parallel_hashmap/btree.h
@@ -163,91 +163,6 @@ namespace phmap {
             bool, type_traits_internal::is_trivially_copyable_impl<T>::kValue> {};
     }  // namespace type_traits_internal
 
-    // -----------------------------------------------------------------------------
-    // C++14 "_t" trait aliases
-    // -----------------------------------------------------------------------------
-
-    template <typename T>
-    using remove_cv_t = typename std::remove_cv<T>::type;
-
-    template <typename T>
-    using remove_const_t = typename std::remove_const<T>::type;
-
-    template <typename T>
-    using remove_volatile_t = typename std::remove_volatile<T>::type;
-
-    template <typename T>
-    using add_cv_t = typename std::add_cv<T>::type;
-
-    template <typename T>
-    using add_const_t = typename std::add_const<T>::type;
-
-    template <typename T>
-    using add_volatile_t = typename std::add_volatile<T>::type;
-
-    template <typename T>
-    using remove_reference_t = typename std::remove_reference<T>::type;
-
-    template <typename T>
-    using add_lvalue_reference_t = typename std::add_lvalue_reference<T>::type;
-
-    template <typename T>
-    using add_rvalue_reference_t = typename std::add_rvalue_reference<T>::type;
-
-    template <typename T>
-    using remove_pointer_t = typename std::remove_pointer<T>::type;
-
-    template <typename T>
-    using add_pointer_t = typename std::add_pointer<T>::type;
-
-    template <typename T>
-    using make_signed_t = typename std::make_signed<T>::type;
-
-    template <typename T>
-    using make_unsigned_t = typename std::make_unsigned<T>::type;
-
-    template <typename T>
-    using remove_extent_t = typename std::remove_extent<T>::type;
-
-    template <typename T>
-    using remove_all_extents_t = typename std::remove_all_extents<T>::type;
-
-    template <size_t Len, size_t Align = type_traits_internal::
-              default_alignment_of_aligned_storage<Len>::value>
-    using aligned_storage_t = typename std::aligned_storage<Len, Align>::type;
-
-    template <typename T>
-    using decay_t = typename std::decay<T>::type;
-
-    template <bool B, typename T = void>
-    using enable_if_t = typename std::enable_if<B, T>::type;
-
-    template <bool B, typename T, typename F>
-    using conditional_t = typename std::conditional<B, T, F>::type;
-
-    template <typename... T>
-    using common_type_t = typename std::common_type<T...>::type;
-
-    template <typename T>
-    using underlying_type_t = typename std::underlying_type<T>::type;
-
-    template <typename T>
-    using result_of_t = typename std::result_of<T>::type;
-
-    namespace type_traits_internal {
-        // In MSVC we can't probe std::hash or stdext::hash because it triggers a
-        // static_assert instead of failing substitution. Libc++ prior to 4.0
-        // also used a static_assert.
-        //
-#if defined(_MSC_VER) || (defined(_LIBCPP_VERSION) &&                   \
-                          _LIBCPP_VERSION < 4000 && _LIBCPP_STD_VER > 11)
-    #define PHMAP_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_ 0
-#else
-    #define PHMAP_META_INTERNAL_STD_HASH_SFINAE_FRIENDLY_ 1
-#endif
-
-    }  // namespace type_traits_internal
-
     namespace swap_internal {
 
         // Necessary for the traits.
diff --git a/parallel_hashmap/phmap_base.h b/parallel_hashmap/phmap_base.h
index 287216d..895216c 100644
--- a/parallel_hashmap/phmap_base.h
+++ b/parallel_hashmap/phmap_base.h
@@ -447,6 +447,16 @@ using enable_if_t = typename std::enable_if<B, T>::type;
 template <bool B, typename T, typename F>
 using conditional_t = typename std::conditional<B, T, F>::type;
 
+
+template <typename... T>
+using common_type_t = typename std::common_type<T...>::type;
+
+template <typename T>
+using underlying_type_t = typename std::underlying_type<T>::type;
+
+template <typename T>
+using result_of_t = typename std::result_of<T>::type;
+
 namespace type_traits_internal {
 
 // ----------------------------------------------------------------------