Hi Robert, After tracking down a linker error I realized that #include <boost/archive/impl/archive_pointer_oserializer.ipp> #include <boost/archive/impl/archive_pointer_iserializer.ipp> need to be included for all new archives that a user might develop, in order to allow serialization of pointers. Are there other such *.ipp files that an archive developer needs to watch out for? Matthias