diff --git a/libcxx/include/__memory/allocator.h b/libcxx/include/__memory/allocator.h
--- a/libcxx/include/__memory/allocator.h
+++ b/libcxx/include/__memory/allocator.h
@@ -27,7 +27,7 @@
 
 template <class _Tp> class allocator;
 
-#if _LIBCPP_STD_VER <= 17
+#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS)
 template <>
 class _LIBCPP_TEMPLATE_VIS allocator<void>
 {
diff --git a/libcxx/test/std/utilities/memory/default.allocator/allocator_types.void.compile.cxx20_with_removed_members.pass.cpp b/libcxx/test/std/utilities/memory/default.allocator/allocator_types.void.compile.cxx20_with_removed_members.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/utilities/memory/default.allocator/allocator_types.void.compile.cxx20_with_removed_members.pass.cpp
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Check that the nested types of std::allocator<void> are provided in C++20
+// with a flag that keeps the removed members.
+
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS
+
+#include <memory>
+#include <type_traits>
+
+int main() {
+  static_assert((std::is_same<std::allocator<void>::pointer, void*>::value), "");
+  static_assert((std::is_same<std::allocator<void>::const_pointer, const void*>::value), "");
+  static_assert((std::is_same<std::allocator<void>::value_type, void>::value), "");
+  static_assert((std::is_same<std::allocator<void>::rebind<int>::other, std::allocator<int> >::value), "");
+}