https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69354
--- Comment #3 from Anthony Williams <anthony.ajw at gmail dot com> --- I hadn't noticed I had omitted the const! Surely the intent of 12.8p11.2 is that if you can't actually copy the bases and/or members with the specified signature then the defaulted copy constructor is deleted? Are you going to file the DR or shall I? Potential core defect aside, I still think this class should work with std::thread, as it fits the MoveConstructible requirement.