diff --git a/docs/source/tutorial/customization.rst b/docs/source/tutorial/customization.rst
index 5479c804..d17379bf 100644
--- a/docs/source/tutorial/customization.rst
+++ b/docs/source/tutorial/customization.rst
@@ -24,6 +24,11 @@ These are template class/structs, so you'll override them using a technique C++
 		template <>
 		struct lua_size<two_things> : std::integral_constant<int, 2> {};
 
+		// Then, specialize the type to match:
+		// this has multiple types, so we consider it a "poly" type.
+		template <>
+		struct lua_type_of<two_things> : std::integral_constant<sol::type, sol::type::poly> {};
+
 		// Now, specialize various stack structures
 		namespace stack {
 
diff --git a/examples/customization.cpp b/examples/customization.cpp
index 45280e59..f9228951 100644
--- a/examples/customization.cpp
+++ b/examples/customization.cpp
@@ -16,6 +16,11 @@ namespace sol {
 	template <>
 	struct lua_size<two_things> : std::integral_constant<int, 2> {};
 
+	// Then, specialize the type
+	// this makes sure Sol can return it properly
+	template <>
+	struct lua_type_of<two_things> : std::integral_constant<sol::type, sol::type::poly> {};
+
 	// Now, specialize various stack structures
 	namespace stack {
 
@@ -67,22 +72,24 @@ namespace sol {
 }
 
 int main() {
+	std::cout << "=== customization example ===" << std::endl;
+	std::cout << std::boolalpha;
+	
 	sol::state lua;
+	lua.open_libraries(sol::lib::base);
 
 	// Create a pass-through style of function
-	lua.script("function f ( a, b ) return a, b end");
+	lua.script("function f ( a, b ) print(a, b) return a, b end");
 
 	// get the function out of Lua
 	sol::function f = lua["f"];
 
-	two_things things = f(two_things{ 24, true });
+	two_things things = f(two_things{ 24, false });
 	assert(things.a == 24);
-	assert(things.b == true);
+	assert(things.b == false);
 	// things.a == 24
 	// things.b == true
 
-	std::cout << "=== customization example ===" << std::endl;
-	std::cout << std::boolalpha;
 	std::cout << "things.a: " << things.a << std::endl;
 	std::cout << "things.b: " << things.b << std::endl;
 	std::cout << std::endl;
diff --git a/single/sol/sol.hpp b/single/sol/sol.hpp
index 75de773e..34709d82 100644
--- a/single/sol/sol.hpp
+++ b/single/sol/sol.hpp
@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2017-02-20 08:45:30.715552 UTC
-// This header was generated with sol v2.15.9 (revision b7b6366)
+// Generated 2017-02-20 23:06:29.737387 UTC
+// This header was generated with sol v2.15.9 (revision 889a45d)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -3686,10 +3686,14 @@ namespace sol {
 	struct is_unique_usertype : std::integral_constant<bool, unique_usertype_traits<T>::value> {};
 
 	template <typename T>
-	struct lua_type_of : detail::lua_type_of<T> {};
+	struct lua_type_of : detail::lua_type_of<T> {
+		typedef int SOL_INTERNAL_UNSPECIALIZED_MARKER_;
+	};
 
 	template <typename T>
-	struct lua_size : std::integral_constant<int, 1> { };
+	struct lua_size : std::integral_constant<int, 1> { 
+		typedef int SOL_INTERNAL_UNSPECIALIZED_MARKER_; 
+	};
 
 	template <typename A, typename B>
 	struct lua_size<std::pair<A, B>> : std::integral_constant<int, lua_size<A>::value + lua_size<B>::value> { };
@@ -3697,10 +3701,24 @@ namespace sol {
 	template <typename... Args>
 	struct lua_size<std::tuple<Args...>> : std::integral_constant<int, detail::accumulate<int, 0, lua_size, Args...>::value> { };
 
+	namespace detail {
+		template <typename...>
+		struct void_ { typedef void type; };
+		template <typename T, typename = void>
+		struct has_internal_marker_impl : std::false_type {};
+		template <typename T>
+		struct has_internal_marker_impl<T, typename void_<typename T::SOL_INTERNAL_UNSPECIALIZED_MARKER_>::type> : std::true_type {};
+
+		template <typename T>
+		struct has_internal_marker : has_internal_marker_impl<T> {};
+	}
+
 	template <typename T>
 	struct is_lua_primitive : std::integral_constant<bool,
 		type::userdata != lua_type_of<meta::unqualified_t<T>>::value
-		|| (lua_size<T>::value > 1)
+		|| ((type::userdata == lua_type_of<meta::unqualified_t<T>>::value) 
+			&& detail::has_internal_marker<lua_type_of<meta::unqualified_t<T>>>::value 
+			&& !detail::has_internal_marker<lua_size<meta::unqualified_t<T>>>::value)
 		|| std::is_base_of<reference, meta::unqualified_t<T>>::value
 		|| std::is_base_of<stack_reference, meta::unqualified_t<T>>::value
 		|| meta::is_specialization_of<std::tuple, meta::unqualified_t<T>>::value
diff --git a/sol/types.hpp b/sol/types.hpp
index be4b5b87..843b2503 100644
--- a/sol/types.hpp
+++ b/sol/types.hpp
@@ -704,10 +704,14 @@ namespace sol {
 	struct is_unique_usertype : std::integral_constant<bool, unique_usertype_traits<T>::value> {};
 
 	template <typename T>
-	struct lua_type_of : detail::lua_type_of<T> {};
+	struct lua_type_of : detail::lua_type_of<T> {
+		typedef int SOL_INTERNAL_UNSPECIALIZED_MARKER_;
+	};
 
 	template <typename T>
-	struct lua_size : std::integral_constant<int, 1> { };
+	struct lua_size : std::integral_constant<int, 1> { 
+		typedef int SOL_INTERNAL_UNSPECIALIZED_MARKER_; 
+	};
 
 	template <typename A, typename B>
 	struct lua_size<std::pair<A, B>> : std::integral_constant<int, lua_size<A>::value + lua_size<B>::value> { };
@@ -715,10 +719,24 @@ namespace sol {
 	template <typename... Args>
 	struct lua_size<std::tuple<Args...>> : std::integral_constant<int, detail::accumulate<int, 0, lua_size, Args...>::value> { };
 
+	namespace detail {
+		template <typename...>
+		struct void_ { typedef void type; };
+		template <typename T, typename = void>
+		struct has_internal_marker_impl : std::false_type {};
+		template <typename T>
+		struct has_internal_marker_impl<T, typename void_<typename T::SOL_INTERNAL_UNSPECIALIZED_MARKER_>::type> : std::true_type {};
+
+		template <typename T>
+		struct has_internal_marker : has_internal_marker_impl<T> {};
+	}
+
 	template <typename T>
 	struct is_lua_primitive : std::integral_constant<bool,
 		type::userdata != lua_type_of<meta::unqualified_t<T>>::value
-		|| (lua_size<T>::value > 1)
+		|| ((type::userdata == lua_type_of<meta::unqualified_t<T>>::value) 
+			&& detail::has_internal_marker<lua_type_of<meta::unqualified_t<T>>>::value 
+			&& !detail::has_internal_marker<lua_size<meta::unqualified_t<T>>>::value)
 		|| std::is_base_of<reference, meta::unqualified_t<T>>::value
 		|| std::is_base_of<stack_reference, meta::unqualified_t<T>>::value
 		|| meta::is_specialization_of<std::tuple, meta::unqualified_t<T>>::value