I did some more research and it turns out std-style piecewise construction fails with VS2012 Nov CTP compiler, just like my attempt at adding piecewise construction to boost::container_detail::pair. In particular, the following dummy code compiles under g++ 4.7.1 but not under VS2012 Nov CTP. class Foo { public: template <class... Args1, class... Args2> Foo( const ::std::piecewise_construct_t, ::std::tuple<Args1...> first_args, ::std::tuple<Args2...> second_args) { } }; int main(){ Foo s( std::piecewise_construct, std::move( std::make_tuple(30) ), std::move( std::make_tuple(50) )); } I guess the time is not ripe for the container implementation to use true variadic templates yet. Is there ongoing effort to implement container_detail::pair's piecewise constructor in the same way as it was implemented in boost::unordered? Best regards, Laszlo Szecsi