If you continue to have problems, please don't hesitate to post a repro.
Here it is: #include <boost/statechart/state_machine.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/statechart/event.hpp> #include <boost/statechart/in_state_reaction.hpp> namespace sc = boost::statechart; struct Event1 : sc::event<Event1> {}; template<class Derived, class Outer> struct ActiveBase : sc::simple_state<Derived, Outer> { void f(const Event1 &) {} }; struct Active; struct FSM : sc::state_machine<FSM, Active> { }; struct Active : ActiveBase<Active, FSM> { typedef sc::in_state_reaction<Event1, ActiveBase, &ActiveBase::f> reactions; }; int main() { FSM fsm; fsm.initiate(); } MSVC9.0, WinXP. 1>...\boost\statechart\state_machine.hpp(493) : error C2440: 'return' : cannot convert from 'FSM' to 'ActiveBase<Derived,Outer> &' 1> with 1> [ 1> Derived=Active, 1> Outer=FSM 1> ]