The trunk version of portable_binary_iarchive.hpp has the following at line 98: // default fall through for any types not specified here template<class T> void load(T & t){ boost::intmax_t l; load_impl(l, sizeof(T)); // use cast to avoid compile time warning t = static_cast<T>(l); } On msvc 8 I get the following warning: F:\Gene_Codes\External_Libraries\boost_1_34_1\boost/archive/portable_binary_iarchive.hpp(103) : warning C4800: 'boost::intmax_t' : forcing value to bool 'true' or 'false' (performance warning) The comment on this function implies that there are specializations somewhere. Would it make sense to have a void load<bool> specialization with: t = l? true : false; Thanks, Jeff