Hi, I've got a project that uses Boost.TR1 (by adding boost/tr1/tr1 to my include path) and Fusion, and i've run into some errors when including the Fusion headers. For example: boost/fusion/tuple/make_tuple.hpp(21) : error C2027: use of undefined type 'boost::fusion::tuple<>' boost/fusion/iterator/prior.hpp(50) : error C2039: 'tag_of' : is not a member of 'boost::fusion::detail' This seems to be caused by the inclusion of <utility> in <boost/fusion/support/tag_of.hpp>, which when using Boost.TR1 like this causes the Fusion headers to be included again. At the point when <utility> is included, the tag_of include guard has been defined but tag_of itself hasn't been declared, so nested inclusions of tag_of.hpp do nothing and the build fails. My code builds ok if i either: -Include <utility> myself before Fusion -Remove the include <utility> from tag_of.hpp (it doesnt actually seem to be required - at least, the regression tests all pass with it removed) This seems a bit fragile though. Is there a better way it can be fixed? Thanks, Richard Webb