c++ - is it possible to create an optional promise? - c++11

Question

consider the following code:
#include <future>
#include <boost/optional.hpp>
struct S {
std::promise<int> p;
};
void f() {
boost::optional<S> o = std::move(S());
}
it fails to compile because somewhere deep inside boost::optional implementation it tries to use the copy constructor of S.
is there some way to overcome this and move the promise without copying it?
I tried to explicitly add a move constructor to S
S(S&& s): p(std::move(s.p)) {}
S() = default;
to no avail.
compiler error message:
In file included from /usr/include/boost/optional.hpp:15:0,
from /tmp/iotpromise.cpp:2:
/usr/include/boost/optional/optional.hpp: In instantiation of ‘void boost::optional_detail::optional_base<T>::construct(boost::optional_detail::optional_base<T>::argument_type) [with T = S; boost::optional_detail::optional_base<T>::argument_type = const S&]’:
/usr/include/boost/optional/optional.hpp:230:20: required from ‘boost::optional_detail::optional_base<T>::optional_base(boost::optional_detail::optional_base<T>::argument_type) [with T = S; boost::optional_detail::optional_base<T>::argument_type = const S&]’
/usr/include/boost/optional/optional.hpp:526:46: required from ‘boost::optional<T>::optional(boost::optional<T>::argument_type) [with T = S; boost::optional<T>::argument_type = const S&]’
/tmp/iotpromise.cpp:9:39: required from here
/usr/include/boost/optional/optional.hpp:346:8: error: use of deleted function ‘S::S(const S&)’
new (m_storage.address()) internal_type(val) ;
^
/tmp/iotpromise.cpp:4:8: note: ‘S::S(const S&)’ is implicitly deleted because the default definition would be ill-formed:
struct S {
^
/tmp/iotpromise.cpp:4:8: error: use of deleted function ‘std::promise<_Res>::promise(const std::promise<_Res>&) [with _Res = int]’
In file included from /tmp/iotpromise.cpp:1:0:
/usr/include/c++/4.9/future:977:7: note: declared here
promise(const promise&) = delete;
^
Using Boost 1.55.0, GCC 6.3