Hello, I'm developing custom polymorphic archive and noticed that virtual function save_null_pointer is never called for my archive. I think the problem is in save_pointer_type::invoke (boost/archive/detail/oserializer.hpp): const basic_pointer_oserializer * bpos_ptr = register_type(ar, * t); if(NULL == t){ basic_oarchive & boa = boost::smart_cast_reference<basic_oarchive &>(ar); boa.save_null_pointer(); save_access::end_preamble(ar); return; } save(ar, * t, bpos_ptr); I see no reasons to use smart_cast here. I think, the code sholud be: const basic_pointer_oserializer * bpos_ptr = register_type(ar, * t); if(NULL == t){ ar.save_null_pointer(); save_access::end_preamble(ar); return; } save(ar, * t, bpos_ptr); Please correct this in the next release of library (or explain).