diff --git a/llvm/include/llvm/ADT/None.h b/llvm/include/llvm/ADT/None.h
--- a/llvm/include/llvm/ADT/None.h
+++ b/llvm/include/llvm/ADT/None.h
@@ -16,11 +16,13 @@
 #ifndef LLVM_ADT_NONE_H
 #define LLVM_ADT_NONE_H
 
+#include <optional>
+
 namespace llvm {
 /// A simple null object to allow implicit construction of Optional<T>
 /// and similar types without having to spell out the specialization's name.
-enum class NoneType { None };
-const NoneType None = NoneType::None;
+using NoneType = std::nullopt_t;
+inline constexpr std::nullopt_t None = std::nullopt;
 }
 
 #endif