diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index c9dae9d..5306bc9 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -9,7 +9,6 @@ jobs:
       fail-fast: false
       matrix:
         config:
-        - { os: windows-2016, vs: "Visual Studio 2017" } # https://github.com/actions/virtual-environments/blob/main/images/win/Windows2016-Readme.md#visual-studio-enterprise-2017
         - { os: windows-2019, vs: "Visual Studio 2019" } # https://github.com/actions/virtual-environments/blob/main/images/win/Windows2019-Readme.md#visual-studio-enterprise-2019
         - { os: windows-2022, vs: "Visual Studio 2022" } # https://github.com/actions/virtual-environments/blob/main/images/win/Windows2022-Readme.md#visual-studio-enterprise-2022
         build: [Debug, Release]
diff --git a/README.md b/README.md
index 9d30373..5670807 100644
--- a/README.md
+++ b/README.md
@@ -259,7 +259,7 @@ enum class Color { RED = 2, BLUE = 4, GREEN = 8 };
 
 ## Compiler compatibility
 
-* Clang/LLVM >= 5
+* Clang/LLVM >= 6
 * MSVC++ >= 14.11 / Visual Studio >= 2017
 * Xcode >= 10
 * GCC >= 9
diff --git a/example/example_custom_name.cpp b/example/example_custom_name.cpp
index 6d27b74..0e7451b 100644
--- a/example/example_custom_name.cpp
+++ b/example/example_custom_name.cpp
@@ -29,16 +29,16 @@ enum class Color : int { RED = -10, BLUE = 0, GREEN = 10 };
 // Сustom definitions of names for enum.
 // Specialization of `enum_name` must be injected in `namespace magic_enum::customize`.
 template <>
-constexpr std::string_view magic_enum::customize::enum_name<Color>(Color value) noexcept {
+constexpr magic_enum::customize::customize_t magic_enum::customize::enum_name<Color>(Color value) noexcept {
   switch (value) {
     case Color::RED:
       return "the red color";
     case Color::BLUE:
       return "The BLUE";
     case Color::GREEN:
-      return {}; // Empty string for default value.
+      return invalid_tag;
   }
-  return {}; // Empty string for unknow value.
+  return default_tag;
 }
 
 enum class Numbers : int { One, Two, Three };
@@ -46,26 +46,26 @@ enum class Numbers : int { One, Two, Three };
 // Сustom definitions of names for enum.
 // Specialization of `enum_name` must be injected in `namespace magic_enum::customize`.
 template <>
-constexpr std::string_view magic_enum::customize::enum_name<Numbers>(Numbers value) noexcept {
+constexpr magic_enum::customize::customize_t magic_enum::customize::enum_name<Numbers>(Numbers value) noexcept {
   switch (value) {
     case Numbers::One:
       return "the one";
     default:
-      return {}; // Empty string for default or unknow value.
+      return default_tag;
   }
 }
 
 int main() {
-  std::cout << magic_enum::enum_name(Color::RED) << std::endl; // the red color
-  std::cout << magic_enum::enum_name(Color::BLUE) << std::endl; // The BLUE
-  std::cout << magic_enum::enum_name(Color::GREEN) << std::endl; // GREEN
+  std::cout << magic_enum::enum_name(Color::RED) << std::endl; // 'the red color'
+  std::cout << magic_enum::enum_name(Color::BLUE) << std::endl; // 'The BLUE'
+  std::cout << magic_enum::enum_name(Color::GREEN) << std::endl; // ''
 
   std::cout << std::boolalpha;
   std::cout << (magic_enum::enum_cast<Color>("the red color").value() == Color::RED) << std::endl; // true
 
-  std::cout << magic_enum::enum_name(Numbers::One) << std::endl; // the one
-  std::cout << magic_enum::enum_name(Numbers::Two) << std::endl; // Two
-  std::cout << magic_enum::enum_name(Numbers::Three) << std::endl; // Three
+  std::cout << magic_enum::enum_name(Numbers::One) << std::endl; // 'the one'
+  std::cout << magic_enum::enum_name(Numbers::Two) << std::endl; // 'Two'
+  std::cout << magic_enum::enum_name(Numbers::Three) << std::endl; // 'Three'
 
   return 0;
 }
diff --git a/include/magic_enum.hpp b/include/magic_enum.hpp
index 5439e03..7b88bd8 100644
--- a/include/magic_enum.hpp
+++ b/include/magic_enum.hpp
@@ -44,6 +44,7 @@
 #include <limits>
 #include <type_traits>
 #include <utility>
+#include <variant>
 
 #if defined(MAGIC_ENUM_CONFIG_FILE)
 #include MAGIC_ENUM_CONFIG_FILE
@@ -134,10 +135,28 @@ struct enum_range {
 static_assert(MAGIC_ENUM_RANGE_MAX > MAGIC_ENUM_RANGE_MIN, "MAGIC_ENUM_RANGE_MAX must be greater than MAGIC_ENUM_RANGE_MIN.");
 static_assert((MAGIC_ENUM_RANGE_MAX - MAGIC_ENUM_RANGE_MIN) < (std::numeric_limits<std::uint16_t>::max)(), "MAGIC_ENUM_RANGE must be less than UINT16_MAX.");
 
+namespace detail {
+enum class default_customize_tag {};
+enum class invalid_customize_tag {};
+} // namespace magic_enum::customize::detail
+
+using customize_t = std::variant<string_view, detail::default_customize_tag, detail::invalid_customize_tag>;
+
+// Default customize.
+inline constexpr auto default_tag = detail::default_customize_tag{};
+// Invalid customize.
+inline constexpr auto invalid_tag = detail::invalid_customize_tag{};
+
 // If need custom names for enum, add specialization enum_name for necessary enum type.
 template <typename E>
-constexpr string_view enum_name(E) noexcept {
-  return {};
+constexpr customize_t enum_name(E) noexcept {
+  return default_tag;
+}
+
+// If need custom type name for enum, add specialization enum_type_name for necessary enum type.
+template <typename E>
+constexpr customize_t enum_type_name() noexcept {
+  return default_tag;
 }
 
 } // namespace magic_enum::customize
@@ -196,6 +215,8 @@ class static_string {
 template <>
 class static_string<0> {
  public:
+  constexpr explicit static_string() = default;
+
   constexpr explicit static_string(string_view) noexcept {}
 
   constexpr const char* data() const noexcept { return nullptr; }
@@ -343,7 +364,13 @@ template <typename E>
 constexpr auto n() noexcept {
   static_assert(is_enum_v<E>, "magic_enum::detail::n requires enum type.");
 
-  if constexpr (supported<E>::value) {
+  [[maybe_unused]] constexpr auto custom = customize::enum_type_name<E>();
+  static_assert(std::is_same_v<std::decay_t<decltype(custom)>, customize::customize_t>, "magic_enum::customize requires customize_t type.");
+  if constexpr (custom.index() == 0) {
+    constexpr auto name = std::get<string_view>(custom);
+    static_assert(!name.empty(), "magic_enum::customize requires not empty string.");
+    return static_string<name.size()>{name};
+  } else if constexpr (custom.index() == 1 && supported<E>::value) {
 #if defined(__clang__) || defined(__GNUC__)
     constexpr auto name = pretty_name({__PRETTY_FUNCTION__, sizeof(__PRETTY_FUNCTION__) - 2});
 #elif defined(_MSC_VER)
@@ -353,7 +380,7 @@ constexpr auto n() noexcept {
 #endif
     return static_string<name.size()>{name};
   } else {
-    return string_view{}; // Unsupported compiler.
+    return static_string<0>{}; // Unsupported compiler or Invalid customize.
   }
 }
 
@@ -363,23 +390,24 @@ inline constexpr auto type_name_v = n<E>();
 template <typename E, E V>
 constexpr auto n() noexcept {
   static_assert(is_enum_v<E>, "magic_enum::detail::n requires enum type.");
-  [[maybe_unused]] constexpr auto custom_name = customize::enum_name<E>(V);
 
-  if constexpr (custom_name.empty()) {
-    if constexpr (supported<E>::value) {
+  [[maybe_unused]] constexpr auto custom = customize::enum_name<E>(V);
+  static_assert(std::is_same_v<std::decay_t<decltype(custom)>, customize::customize_t>, "magic_enum::customize requires customize_t type.");
+  if constexpr (custom.index() == 0) {
+    constexpr auto name = std::get<string_view>(custom);
+    static_assert(!name.empty(), "magic_enum::customize requires not empty string.");
+    return static_string<name.size()>{name};
+  } else if constexpr (custom.index() == 1 && supported<E>::value) {
 #if defined(__clang__) || defined(__GNUC__)
-      constexpr auto name = pretty_name({__PRETTY_FUNCTION__, sizeof(__PRETTY_FUNCTION__) - 2});
+    constexpr auto name = pretty_name({__PRETTY_FUNCTION__, sizeof(__PRETTY_FUNCTION__) - 2});
 #elif defined(_MSC_VER)
-      constexpr auto name = pretty_name({__FUNCSIG__, sizeof(__FUNCSIG__) - 17});
+    constexpr auto name = pretty_name({__FUNCSIG__, sizeof(__FUNCSIG__) - 17});
 #else
-      constexpr auto name = string_view{};
+    constexpr auto name = string_view{};
 #endif
-      return static_string<name.size()>{name};
-    } else {
-      return string_view{}; // Unsupported compiler.
-    }
+    return static_string<name.size()>{name};
   } else {
-    return static_string<custom_name.size()>{custom_name};
+    return static_string<0>{}; // Unsupported compiler or Invalid customize.
   }
 }
 
@@ -943,7 +971,7 @@ template <auto V>
 template <typename E>
 [[nodiscard]] constexpr auto enum_name(E value) noexcept -> detail::enable_if_enum_t<E, string_view> {
   using D = std::decay_t<E>;
-  if (const auto index = enum_index(value); index.has_value()) {
+  if (const auto index = enum_index(value)) {
     return detail::names_v<D>[*index];
   }
   return {};
@@ -1089,7 +1117,7 @@ template <typename E, typename BinaryPredicate = std::equal_to<char>>
 template <auto V>
 [[nodiscard]] constexpr auto enum_index() noexcept -> detail::enable_if_enum_t<decltype(V), std::size_t> {
   constexpr auto index = enum_index<std::decay_t<decltype(V)>>(V);
-  static_assert(index.has_value(), "magic_enum::enum_index enum value does not have a index.");
+  static_assert(index, "magic_enum::enum_index enum value does not have a index.");
 
   return *index;
 }
@@ -1100,13 +1128,13 @@ template <typename E>
   using D = std::decay_t<E>;
   using U = underlying_type_t<D>;
 
-  return enum_cast<D>(static_cast<U>(value)).has_value();
+  return static_cast<bool>(enum_cast<D>(static_cast<U>(value)));
 }
 
 // Checks whether enum contains enumerator with such integer value.
 template <typename E>
 [[nodiscard]] constexpr auto enum_contains(underlying_type_t<E> value) noexcept -> detail::enable_if_enum_t<E, bool> {
-  return enum_cast<std::decay_t<E>>(value).has_value();
+  return static_cast<bool>(enum_cast<std::decay_t<E>>(value));
 }
 
 // Checks whether enum contains enumerator with such name.
@@ -1114,15 +1142,15 @@ template <typename E, typename BinaryPredicate = std::equal_to<char>>
 [[nodiscard]] constexpr auto enum_contains(string_view value, BinaryPredicate p = {}) noexcept(std::is_nothrow_invocable_r_v<bool, BinaryPredicate, char, char>) -> detail::enable_if_enum_t<E, bool> {
   static_assert(std::is_invocable_r_v<bool, BinaryPredicate, char, char>, "magic_enum::enum_contains requires bool(char, char) invocable predicate.");
 
-  return enum_cast<std::decay_t<E>>(value, std::move_if_noexcept(p)).has_value();
+  return static_cast<bool>(enum_cast<std::decay_t<E>>(value, std::move_if_noexcept(p)));
 }
 
 namespace detail {
 
 template <typename E>
 constexpr optional<std::uintmax_t> fuse_one_enum(optional<std::uintmax_t> hash, E value) noexcept {
-  if (hash.has_value()) {
-    if (const auto index = enum_index(value); index.has_value()) {
+  if (hash) {
+    if (const auto index = enum_index(value)) {
       return (*hash << log2(enum_count<E>() + 1)) | *index;
     }
   }
@@ -1143,7 +1171,7 @@ template <typename... Es>
 constexpr auto typesafe_fuse_enum(Es... values) noexcept {
   enum class enum_fuse_t : std::uintmax_t;
   const auto fuse = fuse_enum(values...);
-  if (fuse.has_value()) {
+  if (fuse) {
     return optional<enum_fuse_t>{static_cast<enum_fuse_t>(*fuse)};
   }
   return optional<enum_fuse_t>{};
@@ -1162,7 +1190,7 @@ template <typename... Es>
 #else
   const auto fuse = detail::typesafe_fuse_enum<std::decay_t<Es>...>(values...);
 #endif
-  return assert(fuse.has_value()), fuse;
+  return assert(fuse), fuse;
 }
 
 namespace ostream_operators {
@@ -1185,7 +1213,7 @@ std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& o
 
 template <typename Char, typename Traits, typename E, detail::enable_if_enum_t<E, int> = 0>
 std::basic_ostream<Char, Traits>& operator<<(std::basic_ostream<Char, Traits>& os, optional<E> value) {
-  return value.has_value() ? (os << *value) : os;
+  return value ? (os << *value) : os;
 }
 
 } // namespace magic_enum::ostream_operators
diff --git a/test/test.cpp b/test/test.cpp
index a3d1d49..1b9f219 100644
--- a/test/test.cpp
+++ b/test/test.cpp
@@ -35,6 +35,15 @@
 #include <sstream>
 
 enum class Color { RED = -12, GREEN = 7, BLUE = 15 };
+template <>
+constexpr magic_enum::customize::customize_t magic_enum::customize::enum_name<Color>(Color value) noexcept {
+  switch (value) {
+    case Color::RED:
+      return "red";
+    default:
+      return default_tag;
+  }
+}
 
 enum class Numbers : int { one = 1, two, three, many = 127 };
 
@@ -94,16 +103,6 @@ struct magic_enum::customize::enum_range<Binary> {
   static constexpr int max = 64;
 };
 
-template <>
-constexpr std::string_view magic_enum::customize::enum_name<Color>(Color value) noexcept {
-  switch (value) {
-    case Color::RED:
-      return "red";
-    default:
-      return {};
-  }
-}
-
 using namespace magic_enum;
 
 static_assert(is_magic_enum_supported, "magic_enum: Unsupported compiler (https://github.com/Neargye/magic_enum#compiler-compatibility).");