Hi, If i compile with -DBOOST_SYSTEM_NO_DEPRECATED and #include The compile will fail with the message: boost/filesystem/convenience.hpp: In function ‘typename boost::enable_if::type boost::filesystem::create_directories(const Path&)’: boost/filesystem/convenience.hpp:48: error: ‘posix’ is not a member of ‘boost::system’ BOOST_FS_FUNC(bool) create_directories(const Path& ph) { if (ph.empty() || exists(ph)) { if ( !ph.empty() && !is_directory(ph) ) boost::throw_exception( basic_filesystem_error<Path>( "boost::filesystem::create_directories", ph, make_error_code( boost::system::posix::file_exists ) ) ); return false; } The line with boost::system::posix::file_exists is the key problem. In boost/system/error_code.hpp, posix is defined as a namespace # ifndef BOOST_SYSTEM_NO_DEPRECATED namespace posix = errc; namespace posix_error = errc; # endif but ONLY if I don't define NO_DEPRECATED... Maybe time for regression tests with BOOST_SYSTEM_NO_DEPRECATED defined? thanks, Paul