Greetings! Firstly, this is not a regression, the behaviour was present in 1.30, too. I have attached a simple program that should demonstrate the behaviour, but the core is these lines, with foo being derived from enable_shared_from_this: // 1 std::auto_ptr<foo> g(new foo); boost::shared_ptr<foo> f(g); // 2 std::auto_ptr<foo> g(new foo); boost::shared_ptr<foo const> f(g); // 3 std::auto_ptr<foo const> g(new foo); boost::shared_ptr<foo const> f(g); In all three cases, I'd expect to be able to call shared_from_this(). However, only the first two cases really work. I think it boils down to the function detail::sp_enable_shared_from_this() in the ctor of shared_ptr<> that takes an auto_ptr<>. I'm not certain if there is a fix for this and what that fix would be, but I think the problem is that the 'right' function is not taken because at one place we have a 'foo' and at the other we have a 'foo const'. BTW: I believe that a conversion from auto_ptr<T> to shared_ptr<T const> doesn't compile on VC6, but I can't test that ATM(I'm not at work). If any kind soul wants to, they could add such a conversion to the regression-tests. Same goes for volatile probably. greetings and thumbs up Ulrich Eckhardt