As said before I'm upgrading to V2 and adapting my code accordingly. I have a problem I can't figure what exactly is the source (I'm using VS2012 Update1): namespace blog = boost::log; namespace expr = blog::expressions; const auto FORMAT_MODULE_NAME = expr::attr< std::string >( logattr::MODULE_NAME ); const auto FORMAT_TIMESTAMP = expr::format_date_timeboost::posix_time::ptime( logattr::TIMESTAMP, "%Y-%m-%d %H:%M:%S" ); const auto FORMAT_MESSAGE = expr::message; const auto a = expr::stream << FORMAT_TIMESTAMP; // compiles const auto c = expr::stream << FORMAT_MODULE_NAME; // compiles const auto d = expr::stream << FORMAT_MESSAGE; // error: no operator "<<" matches these operand const auto e = expr::stream << "test"; // error: no operator "<<" matches these operand const auto f = expr::stream << std::string("test"); // error: no operator "<<" matches these operand Any idea what I'm missing? It was working with previous versions. Joel Lamotte