This used to work with 1.32.0, but is failing with cvs. In mersenne_twister.hpp, I add template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & x; ar & i; } Now compile: g++4 -g -DNDEBUG -O3 -ftree-vectorize -msse2 -ffast-math -fstrict-aliasing -Wall -fPIC -I/usr/local/src/boost.cvs -I/usr/include/python2.4 -I/home/\ nbecker/shannon2.darcs/src -c -o boost_rand.os boost_rand.cc /usr/local/src/boost.cvs/boost/archive/detail/oserializer.hpp: In function 'void boost::archive::save(Archive&, T&) [with Archive = boost::archive:\ :binary_oarchive, T = boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18, 3346425566u\
]': /usr/local/src/boost.cvs/boost/archive/basic_binary_oarchive.hpp:69: instantiated from 'void boost::archive::basic_binary_oarchive<Archive>::save\ _override(T&, int) [with T = boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18, 3346\ 425566u>, Archive = boost::archive::binary_oarchive]' /usr/local/src/boost.cvs/boost/archive/binary_oarchive.hpp:47: instantiated from 'void boost::archive::binary_oarchive_impl<Archive>::save_overri\ de(T&, int) [with T = boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18, 3346425566u\ , Archive = boost::archive::binary_oarchive]' /usr/local/src/boost.cvs/boost/archive/detail/interface_oarchive.hpp:89: instantiated from 'Archive& boost::archive::detail::interface_oarchive<A\ rchive>::operator<<(T&) [with T = boost::random::mersenne_twister<uint32_t, 32, 624, 397, 31, 2567483615u, 11, 7, 2636928640u, 15, 4022730752u, 18,\ 3346425566u>, Archive = boost::archive::binary_oarchive]' boost_rand.cc:41: instantiated from here /usr/local/src/boost.cvs/boost/archive/detail/oserializer.hpp:557: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTI\ ON_FAILURE<false>'