Hi Neil, the fix for #9851 broke some of our code. We use chained range adaptors like std::vector<std::string> separated std::set<Foo> foos; boost::copy(separated | boost::adaptors::transformed(boost::bind(Foo::fromString, _1)) | boost::adaptors::filtered(boost::bind(&Foo::isValid, _1)), std::inserter(foos, foos.end())); which fails with error: constructor for 'boost::transform_iterator<boost::_bi::bind_t<Foo, Foo (*)(const std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > &), boost::_bi::list1<boost::arg<1> > >, std::__1::__wrap_iter<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > *>, boost::use_default, boost::use_default>' must explicitly initialize the member 'm_f' which does not have a default constructor transform_iterator() { } Full testcase and error message attached. This compiles and works with 1.55.0. git bisect shows that this fails to compile from 5f2560f - Ticket 9851 - adaptors should perform concept check assertions. for gcc and for clang starting with e43796c - allow clang to use Range Concepts despite reporting GCC 4.2. msvc-12.0 fails, too. gcc-4.8.2 and clang-3.5 (trunk) for the record. Any chance to get this fixed for 1.56.0 ? Yours, Jürgen -- * Dipl.-Math. Jürgen Hunold ! * voice: ++49 4257 300 ! Fährstraße 1 * fax : ++49 4257 300 ! 31609 Balge/Sebbenhausen * jhunold@gmx.eu ! Germany