Index: include/tuple
===================================================================
--- include/tuple
+++ include/tuple
@@ -706,7 +706,7 @@
               typename enable_if
                       <
                          _CheckArgsConstructor<
-                             sizeof...(_Up) <= sizeof...(_Tp)
+                             sizeof...(_Up) == sizeof...(_Tp)
                              && !_PackExpandsToThisTuple<_Up...>::value
                          >::template __enable_implicit<_Up...>(),
                          bool
@@ -716,17 +716,17 @@
         tuple(_Up&&... __u)
             _NOEXCEPT_((
                 is_nothrow_constructible<base,
-                    typename __make_tuple_indices<sizeof...(_Up)>::type,
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
+                    typename __make_tuple_indices<sizeof...(_Tp)>::type,
+                    __tuple_types<_Tp...>,
+                    __tuple_indices<>,
+                    __tuple_types<>,
                     _Up...
                 >::value
             ))
-            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
-                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
-                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
+            : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type{},
+                    __tuple_types<_Tp...>{},
+                    __tuple_indices<>{},
+                    __tuple_types<>{},
                     _VSTD::forward<_Up>(__u)...) {}
 
     template <class ..._Up,
@@ -735,7 +735,11 @@
                          _CheckArgsConstructor<
                              sizeof...(_Up) <= sizeof...(_Tp)
                              && !_PackExpandsToThisTuple<_Up...>::value
-                         >::template __enable_explicit<_Up...>(),
+                         >::template __enable_explicit<_Up...>()  ||
+                         _CheckArgsConstructor<
+                             sizeof...(_Up) < sizeof...(_Tp)
+                             && !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_implicit<_Up...>(),
                          bool
                       >::type = false
              >