diff --git a/src/emu/input.h b/src/emu/input.h
index 78383e68ae9..dc76a4a0adb 100644
--- a/src/emu/input.h
+++ b/src/emu/input.h
@@ -24,6 +24,7 @@
 #include <map>
 #include <memory>
 #include <string>
+#include <utility>
 
 
 //**************************************************************************
@@ -433,14 +434,8 @@ class input_seq
 {
 public:
 	// construction/destruction
-	constexpr input_seq() noexcept
-	{
-		reset();
-	}
-	template <typename... T> constexpr input_seq(input_code code_0, T... code_n) noexcept
-	{
-		set(code_0, code_n...);
-	}
+	constexpr input_seq() noexcept : input_seq(std::make_index_sequence<std::tuple_size<decltype(m_code)>::value>()) { }
+	template <typename... T> constexpr input_seq(input_code code_0, T... code_n) noexcept : input_seq(std::make_index_sequence<std::tuple_size<decltype(m_code)>::value - sizeof...(T) - 1>(), code_0, code_n...) { }
 	constexpr input_seq(const input_seq &rhs) noexcept = default;
 
 	// operators
@@ -478,6 +473,10 @@ public:
 	static const input_seq empty_seq;
 
 private:
+	static constexpr input_code get_end_code(size_t) noexcept { return end_code; }
+
+	template <typename... T, size_t... N> constexpr input_seq(std::integer_sequence<size_t, N...>, T... code) noexcept : m_code({ code..., get_end_code(N)... }) { }
+
 	template <unsigned N> void set() noexcept
 	{
 		std::fill(std::next(m_code.begin(), N), m_code.end(), end_code);