diff --git a/include/cppast/cpp_enum.hpp b/include/cppast/cpp_enum.hpp
index aae1965..e8b10d2 100644
--- a/include/cppast/cpp_enum.hpp
+++ b/include/cppast/cpp_enum.hpp
@@ -64,9 +64,9 @@ namespace cppast
         {
         public:
             /// \effects Sets the name, underlying type and whether it is scoped.
-            /// \notes The underlying type may be `nullptr` if it is not explictly given.
-            builder(std::string name, bool scoped, std::unique_ptr<cpp_type> type = nullptr)
-            : enum_(new cpp_enum(std::move(name), std::move(type), scoped))
+            builder(std::string name, bool scoped, std::unique_ptr<cpp_type> type,
+                    bool explicit_type)
+            : enum_(new cpp_enum(std::move(name), std::move(type), explicit_type, scoped))
             {
             }
 
@@ -105,11 +105,16 @@ namespace cppast
             std::unique_ptr<cpp_enum> enum_;
         };
 
-        /// \returns A [ts::optional_ref]() to the underlying [cppast::cpp_type]() of the enum.
-        /// \notes It only has an associated underlying type if it is not explictly given.
-        type_safe::optional_ref<const cpp_type> underlying_type() const noexcept
+        /// \returns A reference to the underlying [cppast::cpp_type]() of the enum.
+        const cpp_type& underlying_type() const noexcept
         {
-            return type_safe::opt_cref(type_.get());
+            return *type_;
+        }
+
+        /// \returns Whether or not the underlying type is explictly given.
+        bool has_explicit_type() const noexcept
+        {
+            return type_given_;
         }
 
         /// \returns Whether or not it is a scoped enumeration (i.e. an `enum class`).
@@ -119,8 +124,11 @@ namespace cppast
         }
 
     private:
-        cpp_enum(std::string name, std::unique_ptr<cpp_type> type, bool scoped)
-        : cpp_entity(std::move(name)), type_(std::move(type)), scoped_(scoped)
+        cpp_enum(std::string name, std::unique_ptr<cpp_type> type, bool type_given, bool scoped)
+        : cpp_entity(std::move(name)),
+          type_(std::move(type)),
+          scoped_(scoped),
+          type_given_(type_given)
         {
         }
 
@@ -131,7 +139,7 @@ namespace cppast
         type_safe::optional<std::string> do_get_scope_name() const override;
 
         std::unique_ptr<cpp_type> type_;
-        bool                      scoped_;
+        bool                      scoped_, type_given_;
     };
 } // namespace cppast
 
diff --git a/src/code_generator.cpp b/src/code_generator.cpp
index 337357a..07a0645 100644
--- a/src/code_generator.cpp
+++ b/src/code_generator.cpp
@@ -205,10 +205,10 @@ namespace
             if (e.is_scoped())
                 output << whitespace << keyword("class");
             output << whitespace << identifier(e.name());
-            if (e.underlying_type())
+            if (e.has_explicit_type())
             {
                 output << newl << punctuation(":");
-                detail::write_type(output, e.underlying_type().value(), "");
+                detail::write_type(output, e.underlying_type(), "");
             }
 
             if (e.is_definition())
diff --git a/src/libclang/enum_parser.cpp b/src/libclang/enum_parser.cpp
index 45d59fe..bcb4e3d 100644
--- a/src/libclang/enum_parser.cpp
+++ b/src/libclang/enum_parser.cpp
@@ -53,12 +53,11 @@ namespace
         detail::skip_attribute(stream);
         auto& name = stream.get().value();
 
-        std::unique_ptr<cpp_type> type;
-        if (detail::skip_if(stream, ":"))
-            // parse type, explictly given one
-            type = detail::parse_type(context, cur, clang_getEnumDeclIntegerType(cur));
+        // parse type
+        auto type       = detail::parse_type(context, cur, clang_getEnumDeclIntegerType(cur));
+        auto type_given = detail::skip_if(stream, ":");
 
-        return cpp_enum::builder(name.c_str(), scoped, std::move(type));
+        return cpp_enum::builder(name.c_str(), scoped, std::move(type), type_given);
     }
 }
 
diff --git a/test/cpp_enum.cpp b/test/cpp_enum.cpp
index f6153e0..8b7c96c 100644
--- a/test/cpp_enum.cpp
+++ b/test/cpp_enum.cpp
@@ -54,7 +54,7 @@ enum c : int;
             REQUIRE(e.is_definition());
             REQUIRE(!e.is_declaration());
             REQUIRE(!e.is_scoped());
-            REQUIRE(!e.underlying_type());
+            REQUIRE(!e.has_explicit_type());
 
             auto no_vals = 0u;
             for (auto& val : e)
@@ -96,9 +96,8 @@ enum c : int;
 
             if (e.is_definition())
             {
-                REQUIRE(e.underlying_type());
-                REQUIRE(equal_types(idx, e.underlying_type().value(),
-                                    *cpp_builtin_type::build(cpp_int)));
+                REQUIRE(e.has_explicit_type());
+                REQUIRE(equal_types(idx, e.underlying_type(), *cpp_builtin_type::build(cpp_int)));
 
                 auto no_vals = 0u;
                 for (auto& val : e)
@@ -125,7 +124,7 @@ enum c : int;
             }
             else if (e.is_declaration())
             {
-                REQUIRE(!e.underlying_type()); // no underlying type, implicit int
+                REQUIRE(!e.has_explicit_type()); // no underlying type, implicit int
                 REQUIRE(count_children(e) == 0u);
 
                 auto definition = get_definition(idx, e);
@@ -141,9 +140,8 @@ enum c : int;
             REQUIRE(e.is_declaration());
             REQUIRE(!e.is_definition());
             REQUIRE(!e.is_scoped());
-            REQUIRE(e.underlying_type().has_value());
-            REQUIRE(
-                equal_types(idx, e.underlying_type().value(), *cpp_builtin_type::build(cpp_int)));
+            REQUIRE(e.has_explicit_type());
+            REQUIRE(equal_types(idx, e.underlying_type(), *cpp_builtin_type::build(cpp_int)));
             REQUIRE(count_children(e) == 0u);
 
             auto definition = get_definition(idx, e);