diff --git a/include/hfsm2/detail/shared/type_list.hpp b/include/hfsm2/detail/shared/type_list.hpp
index 2a523e6..a5f0f98 100644
--- a/include/hfsm2/detail/shared/type_list.hpp
+++ b/include/hfsm2/detail/shared/type_list.hpp
@@ -25,17 +25,17 @@ using Prepend = typename PrependT<Ts...>::Type;
 
 //------------------------------------------------------------------------------
 
-template <size_t, size_t, typename...>
+template <LongIndex, LongIndex, typename...>
 struct LesserT;
 
-template <size_t H, size_t I, typename TFirst, typename... TRest>
+template <LongIndex H, LongIndex I, typename TFirst, typename... TRest>
 struct LesserT<H, I, TFirst, TRest...> {
 	using Type = typename std::conditional<(I < H),
 										   Prepend<TFirst, typename LesserT<H, I + 1, TRest...>::Type>,
 										   typename LesserT<H, I + 1, TRest...>::Type>::type;
 };
 
-template <size_t H, size_t I>
+template <LongIndex H, LongIndex I>
 struct LesserT<H, I> {
 	using Type = TL_<>;
 };
@@ -45,17 +45,17 @@ using SplitL = typename LesserT<sizeof...(Ts) / 2, 0, Ts...>::Type;
 
 //------------------------------------------------------------------------------
 
-template <size_t, size_t, typename...>
+template <LongIndex, LongIndex, typename...>
 struct GreaterT;
 
-template <size_t H, size_t I, typename TFirst, typename... TRest>
+template <LongIndex H, LongIndex I, typename TFirst, typename... TRest>
 struct GreaterT<H, I, TFirst, TRest...> {
 	using Type = typename std::conditional<(I < H),
 										   typename GreaterT<H, I + 1, TRest...>::Type,
 										   TL_<TFirst, TRest...>>::type;
 };
 
-template <size_t H, size_t I>
+template <LongIndex H, LongIndex I>
 struct GreaterT<H, I> {
 	using Type = TL_<>;
 };
@@ -109,7 +109,7 @@ using IndexSequenceFor = MakeIndexSequence<sizeof...(Ts)>;
 template <typename T>
 struct IndexedTypeList_EntryT {};
 
-template <typename T, std::size_t N>
+template <typename T, LongIndex N>
 struct IndexedTypeList_EntryN
 	: IndexedTypeList_EntryT<T>
 {};
@@ -123,7 +123,7 @@ template <LongIndex... Ns, typename... Ts>
 struct IndexedTypeList_Impl<IndexSequence<Ns...>, Ts...>
 	: IndexedTypeList_EntryN<Ts, Ns>...
 {
-	template <typename T, std::size_t N>
+	template <typename T, LongIndex N>
 	static constexpr LongIndex select(IndexedTypeList_EntryN<T, N>) { return (LongIndex) N; }
 };
 
diff --git a/include/hfsm2/machine.hpp b/include/hfsm2/machine.hpp
index 2ecbefd..537857c 100644
--- a/include/hfsm2/machine.hpp
+++ b/include/hfsm2/machine.hpp
@@ -1687,17 +1687,17 @@ using Prepend = typename PrependT<Ts...>::Type;
 
 //------------------------------------------------------------------------------
 
-template <size_t, size_t, typename...>
+template <LongIndex, LongIndex, typename...>
 struct LesserT;
 
-template <size_t H, size_t I, typename TFirst, typename... TRest>
+template <LongIndex H, LongIndex I, typename TFirst, typename... TRest>
 struct LesserT<H, I, TFirst, TRest...> {
 	using Type = typename std::conditional<(I < H),
 										   Prepend<TFirst, typename LesserT<H, I + 1, TRest...>::Type>,
 										   typename LesserT<H, I + 1, TRest...>::Type>::type;
 };
 
-template <size_t H, size_t I>
+template <LongIndex H, LongIndex I>
 struct LesserT<H, I> {
 	using Type = TL_<>;
 };
@@ -1707,17 +1707,17 @@ using SplitL = typename LesserT<sizeof...(Ts) / 2, 0, Ts...>::Type;
 
 //------------------------------------------------------------------------------
 
-template <size_t, size_t, typename...>
+template <LongIndex, LongIndex, typename...>
 struct GreaterT;
 
-template <size_t H, size_t I, typename TFirst, typename... TRest>
+template <LongIndex H, LongIndex I, typename TFirst, typename... TRest>
 struct GreaterT<H, I, TFirst, TRest...> {
 	using Type = typename std::conditional<(I < H),
 										   typename GreaterT<H, I + 1, TRest...>::Type,
 										   TL_<TFirst, TRest...>>::type;
 };
 
-template <size_t H, size_t I>
+template <LongIndex H, LongIndex I>
 struct GreaterT<H, I> {
 	using Type = TL_<>;
 };
@@ -1771,7 +1771,7 @@ using IndexSequenceFor = MakeIndexSequence<sizeof...(Ts)>;
 template <typename T>
 struct IndexedTypeList_EntryT {};
 
-template <typename T, std::size_t N>
+template <typename T, LongIndex N>
 struct IndexedTypeList_EntryN
 	: IndexedTypeList_EntryT<T>
 {};
@@ -1785,7 +1785,7 @@ template <LongIndex... Ns, typename... Ts>
 struct IndexedTypeList_Impl<IndexSequence<Ns...>, Ts...>
 	: IndexedTypeList_EntryN<Ts, Ns>...
 {
-	template <typename T, std::size_t N>
+	template <typename T, LongIndex N>
 	static constexpr LongIndex select(IndexedTypeList_EntryN<T, N>) { return (LongIndex) N; }
 };
 
diff --git a/test/test_debug.cpp b/test/test_debug.cpp
index 2582eb8..4952203 100644
--- a/test/test_debug.cpp
+++ b/test/test_debug.cpp
@@ -15,7 +15,7 @@ void
 assertStructure(const FSM::Instance::Structure& structure,
 				const StructureReference& reference)
 {
-	const auto count = std::max((size_t) structure.count(), reference.size());
+	const auto count = std::max((std::size_t) structure.count(), reference.size());
 
 	for (uint16_t i = 0; i < count; ++i) {
 		REQUIRE(i < structure.count());
@@ -42,7 +42,7 @@ void
 assertActivity(const FSM::Instance::ActivityHistory& activity,
 			   const ActivityReference& reference)
 {
-	const auto count = std::max((size_t) activity.count(), reference.size());
+	const auto count = std::max((std::size_t) activity.count(), reference.size());
 
 	for (uint16_t i = 0; i < count; ++i) {
 		REQUIRE(i < activity.count());