As far as I can tell, the version number passed into load_construct_data is not actually useful. This conclusion is based (among other things) on the fact that stack_construct (in serialization/detail/stack_constructor.hpp) always calls load_construct_data_adl with 0U for the version argument. This leads me to believe that in the current implementation if I specialize load_construct_data for one of my classes, I can never change it later, as the class version number from the input archive is inaccessible inside load_construct_data. Am I missing something obvious, or is it really the case that versioning doesn't work for load_construct_data right now? Thanks, Ben -- If this message helped you, consider buying an item from my wish list: <http://artins.org/ben/wishlist> I changed my name: <http://periodic-kingdom.org/People/NameChange.php>