Index: include/tuple
===================================================================
--- include/tuple
+++ include/tuple
@@ -751,7 +751,7 @@
                          _CheckArgsConstructor<
                             !_EnableImplicitReducedArityExtension
                             && sizeof...(_Up) < sizeof...(_Tp)
-                            && !_PackExpandsToThisTuple<_Up...>()
+                            && !_PackExpandsToThisTuple<_Up...>::value
                          >::template __enable_implicit<_Up...>(),
                          bool
                       >::type = false
Index: test/std/utilities/tuple/tuple.tuple/tuple.cnstr/reduce_arity_confusion.pass.cpp
===================================================================
--- /dev/null
+++ test/std/utilities/tuple/tuple.tuple/tuple.cnstr/reduce_arity_confusion.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <tuple>
+
+// template <class... Types> class tuple;
+
+// tuple(tuple const&);
+// tuple(tuple&&);
+// template <class... UTypes>
+//   tuple(UTypes&&... u);
+// Check that there is no confusion between reduced arity constructors and
+// copy/move constructors.
+
+// UNSUPPORTED: c++98, c++03
+
+#include <tuple>
+#include <cassert>
+
+struct Empty {};
+
+struct TupleConvertible {
+    TupleConvertible() : value(0) {}
+    TupleConvertible(const std::tuple<TupleConvertible, Empty>&) : value(1) {}
+    TupleConvertible(std::tuple<TupleConvertible, Empty>&&) : value(1) {}
+    TupleConvertible(const TupleConvertible&) : value(2) {}
+    TupleConvertible(TupleConvertible&&) : value(3) {}
+    int value;
+};
+
+int main() {
+    using Tuple = std::tuple<TupleConvertible, Empty>;
+    Tuple x{TupleConvertible(), Empty()};
+    // Test that move constructor is preferred to reduced arity constructor
+    Tuple y(std::move(x));
+    assert(std::get<0>(y).value == 3);
+    // Test that copy constructor is preferred to reduced arity constructor
+    Tuple z1((const Tuple&)y);
+    assert(std::get<0>(z1).value == 2);
+    Tuple z2((Tuple&)y);
+    assert(std::get<0>(z2).value == 2);
+    Tuple z3((const Tuple)y);
+    assert(std::get<0>(z3).value == 2);
+    Tuple z4(y);
+    assert(std::get<0>(z4).value == 2);
+}