Hi, I am attempting to use boost::serialization to serialize a simple derived class to an XML archive. I have no problem creating a text archive - code compiles and the text archive contains both base class and derived class members. If I switch to the boost::archive::xml_oarchive it no longer compiles. Here is the code creating the archive: const DerivedClass obj; std::string filename = "fooBar.xml"; std::ofstream ofs(filename.c_str()); assert(ofs.good()); { boost::archive::xml_oarchive oa(ofs); oa << obj; } Here is the gcc-4.1.2 compiler output (Ubuntu): /usr/local/include/boost-1_34/boost/archive/basic_xml_oarchive.hpp: In member function ‘void boost::archive::basic_xml_oarchive<Archive>::save_override(T&, int) [with T = const DerivedClass, Archive = boost::archive::xml_oarchive]’: /usr/local/include/boost-1_34/boost/archive/detail/interface_oarchive.hpp:79: instantiated from ‘Archive& boost::archive::detail::interface_oarchive<Archive>::operator<<(T&) [with T = const DerivedClass, Archive = boost::archive::xml_oarchive]’ mkevents.cpp:81: instantiated from here /usr/local/include/boost-1_34/boost/archive/basic_xml_oarchive.hpp:83: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’ So I'm wondering if the requirements for using txt_oarchive are different than for xml_oarchive? It seems they should both work the same. Thanks Gerald