A while ago I pointed out that BOOST_EXPLICIT_TEMPLATE_TYPE_SPEC and its three variations (in config/suffix.hpp) are useless for VC6 (the only compiler, IIRC, for which the non-_SPEC versions were introduced). http://article.gmane.org/gmane.comp.lib.boost.devel/23486/ I thought they had been removed but I see that they are still there. There's one usage, in variant/detail/forced_return.hpp. Is it really needed? Why? Genny.