Index: libcxx/include/optional
===================================================================
--- libcxx/include/optional
+++ libcxx/include/optional
@@ -622,7 +622,7 @@
 template <class _Tp> struct __is_std_optional<optional<_Tp>> : true_type {};
 
 template <class _Tp>
-class optional
+class _LIBCPP_DECLSPEC_EMPTY_BASES optional
     : private __optional_move_assign_base<_Tp>
     , private __optional_sfinae_ctor_base_t<_Tp>
     , private __optional_sfinae_assign_base_t<_Tp>
Index: libcxx/include/variant
===================================================================
--- libcxx/include/variant
+++ libcxx/include/variant
@@ -1266,7 +1266,7 @@
 } // namespace __variant_detail
 
 template <class... _Types>
-class _LIBCPP_TEMPLATE_VIS variant
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_DECLSPEC_EMPTY_BASES variant
     : private __sfinae_ctor_base<
           __all<is_copy_constructible_v<_Types>...>::value,
           __all<is_move_constructible_v<_Types>...>::value>,