diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -394,8 +394,6 @@
 # error "We don't know a correct way to implement alignof(T) in C++03 outside of Clang"
 #endif
 
-#define _LIBCPP_PREFERRED_ALIGNOF(_Tp) __alignof(_Tp)
-
 #if defined(_LIBCPP_COMPILER_CLANG_BASED)
 
 #if defined(__APPLE__) && !defined(__i386__) && !defined(__x86_64__) &&       \
diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -747,7 +747,8 @@
 template <class _Tp>
 struct __align_type
 {
-    static const size_t value = _LIBCPP_PREFERRED_ALIGNOF(_Tp);
+    // We want the preferred alignof instead of the minimum, so use __alignof instead
+    static const size_t value = __alignof(_Tp);
     typedef _Tp type;
 };
 
@@ -881,8 +882,9 @@
 template <size_t _Len, class _Type0, class ..._Types>
 struct aligned_union
 {
-    static const size_t alignment_value = __static_max<_LIBCPP_PREFERRED_ALIGNOF(_Type0),
-                                                       _LIBCPP_PREFERRED_ALIGNOF(_Types)...>::value;
+    // We want the preferred alignof instead of the minimum, so use __alignof instead
+    static const size_t alignment_value = __static_max<__alignof(_Type0),
+                                                       __alignof(_Types)...>::value;
     static const size_t __len = __static_max<_Len, sizeof(_Type0),
                                              sizeof(_Types)...>::value;
     typedef typename aligned_storage<__len, alignment_value>::type type;