Seems I can't "unforget" erroneously forgotten files, so will have to forget them and then re-add them
// Copyright David Abrahams 2006. Distributed under the Boost
// Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
# undef BOOST_concept_typename
# undef BOOST_concept