diff --git a/Siv3D/include/Siv3D/detail/Indexed.ipp b/Siv3D/include/Siv3D/detail/Indexed.ipp
index 9c716492b..c07479d80 100644
--- a/Siv3D/include/Siv3D/detail/Indexed.ipp
+++ b/Siv3D/include/Siv3D/detail/Indexed.ipp
@@ -20,8 +20,8 @@ namespace s3d
 
 		struct Iterator
 		{
-			using value_type = std::tuple<Type, typename std::iterator_traits<It>::value_type>;
-			using reference = std::tuple<Type, decltype(*std::declval<It&>())>;
+			using value_type = std::tuple<size_t, typename std::iterator_traits<It>::value_type>;
+			using reference = std::tuple<size_t, decltype(*std::declval<It&>())>;
 			size_t index;
 			It it;
 			constexpr bool operator != (const Iterator& other) const { return it != other.it; }
@@ -50,8 +50,8 @@ namespace s3d
 	{
 		struct Iterator
 		{
-			using value_type = std::tuple<Type, typename std::iterator_traits<It>::value_type>;
-			using reference = std::tuple<Type, decltype(*std::declval<It&>())>;
+			using value_type = std::tuple<size_t, typename std::iterator_traits<It>::value_type>;
+			using reference = std::tuple<size_t, decltype(*std::declval<It&>())>;
 			size_t index;
 			It it;
 			constexpr bool operator != (const Iterator& other) const { return it != other.it; }