thread

I have a boost ASIO deadline timer in a boost thread and I'm trying to cancel the timer from the main thread.

    boost::asio::io_service timer_service;
    boost::asio::deadline_timer timer(timer_service);

    std::unique_ptr<boost::thread> m_thread;

    // ...
    timer_service.reset();
    timer.expires_from_now(boost::posix_time::seconds(20));
    timer.async_wait(my_handler);

    m_thread = unique_ptr<boost::thread>(new boost::thread(boost::bind(&boost::asio::io_service::run, &timer_service)));

From the main thread, I try to cancel it using this lambda, but getting the following compile error.

    case CANCEL:
    {
        // ...
        timer.get_io_service().post([timer] { timer.cancel(); });
        break;
    }


/boost/asio/detail/impl/task_io_service.hpp:56:6:
error: 'void boost::asio::detail::task_io_service::post(Handler&) [with
Handler = main(int, char**)::<lambda()>]', declared using local
type 'main(int, char**)::<lambda()>', is used but never defined
[-fpermissive]
 void task_io_service::post(Handler& handler)
      ^

Anyone see where I'm going wrong?