I recently upgraded from 1.43 to 1.46 and this broke the serialization. We could not read archives save with 1.43. I the investigation i noticed the following issues. 1. in basic_binary_iarchive tracking_type is loaded as integer type or bool, but in basic_binary_oarchive it is stored as primitive type tracking_type. This breaks custom binary archives that have overloads for integer types and bools to be broken this problem probably applies to other internal serialization types (collection_size_type, version_type, etc), but I have not investigated this. 2. I have a custom binary archives which have overloads for integer types (loosely) like: class custom_binary_iarchive : boost::archive::binary_iarchive_impl<custom_binary_iarchive> { };