The code below fails a compile-time assertion in boost 1.32.0 on MSVC 7.1. This is because, internally, boost::optional uses boost::alignment_of, which produces the number 12, which is then passed as a template parameter to boost::type_with_alignment, which won't accept 12. Not sure where the blame lies. Is it with boost::alignment_of, for producing 12 in the first place? Perhaps not, since 12 is a multiple of 4, and the doco says boost::alignment_of is allowed to produce any multiple of the actual alignment value. So is the fault with boost::type_with_alignment, for not accepting 12? Or is there something wrong with the app? #include <boost/optional.hpp> class D { virtual ~D(); }; class E : virtual public D { virtual ~E(); unsigned long long m_i; }; boost::optional<E> s_optE; Cheers, --- Michael Shepanski