Hello. When we serialize a polymorphic object, an archive stores the information about true_type (i.e. the concrete type of an object) only if it is not equal to this_type (i.e. the type of the serialized object). I.e. : the type of the serialized object is stored only if it is serialized from a base class. How can I force the archive to always store the type? Let's illustrate with a sample, I'm not sure the above text is so obvious...: Let's have 2 classes serializable: class Base { ... }; class Leaf : public Base { ... }; If I do : std::stringstream ios(std::ios_base::binary | std::ios_base::out | std::ios_base::in); * Base** b = new *Leaf*(); boost::archive::text_oarchive ar(ios); ar & b; Then the archive contains: 22 serialization::archive 9 0 4 *Leaf* 1 0 0 0 0 0 0 0 0 It contains the Leaf concrete type information. However if I do : * Leaf** b = new *Leaf*(); boost::archive::text_oarchive ar(ios); ar & b; Then the archive contains: 22 serialization::archive 9 0 1 0 0 0 0 0 0 0 0 It doesn't contain Lef type info. How can I produce an archive WITH the true_type all the type? I search 2 ways: - calling a method of archive type (register_type, save_pointer, ...) unsuccessfully - directly change the boost/archive/detail/oserializer.hpp file: in struct polymorphic, in function template<class T> static void save(Archive &ar, T & t) I comment out if(*this_type == *true_type){ const basic_pointer_oserializer * bpos = register_type(ar, t); ar.save_pointer(vp, bpos); return; } unsuccessfully. Thank you for help. Nicolas. PS : a word about why I'm trying to do that. When the true_type is "registered" (I'm not sure register is the right word), we can deserialize the object to any base class. Exemple: SERIALIZATION: Leaf* leaf = new Leaf(); ar & leaf; SERIALIZATION: Base* b = 0; ar & b; // would work only if Leaf has been saved in the archive as true_type For tools in a multi-team project, it' powerfull : data for tests has been serialized by a team, and the other team can deserialize, let's say an image, to the interface class IImage without asking: what was the true_tyep : an Image3D, an AImage2D, an Image2DRGB, an Image2DRAW, and so on.