Hi, This simple call results in errors. boost::fusion::fused<boost::factory<int*> >() (boost::fusion::vector0 ()); Errors in gcc 4.3.2: /opt/i686-cross-gcc-boost_1_38_0/gcc-4.1.2-glibc-2.3.6/i686-unknown-linux-gnu/i686-unknown-linux-gnu/usr/include/boost/fusion/functional/invocation/invoke.hpp: In instantiation of 'boost::fusion::detail::invoke_impl<boost::factory<int*, int boost::detail::none_helper::*, factory_alloc_for_pointee_and_deleter>, boost::fusion::vector0, 0, true, true>': /opt/i686-cross-gcc-boost_1_38_0/gcc-4.1.2-glibc-2.3.6/i686-unknown-linux-gnu/i686-unknown-linux-gnu/usr/include/boost/fusion/functional/invocation/invoke.hpp:80: error: invalid use of undefined type 'struct boost::fusion::detail::invoke_mem_fn<boost::factory<int*, int boost::detail::none_helper::*, factory_alloc_for_pointee_and_deleter>, boost::fusion::vector0, 0, true>' /opt/i686-cross-gcc-boost_1_38_0/gcc-4.1.2-glibc-2.3.6/i686-unknown-linux-gnu/i686-unknown-linux-gnu/usr/include/boost/fusion/functional/invocation/invoke.hpp:89: error: declaration of 'struct boost::fusion::detail::invoke_mem_fn<boost::factory<int*, int boost::detail::none_helper::*, factory_alloc_for_pointee_and_deleter>, boost::fusion::vector0, 0, true>' This seems because CBI in invoke_impl is being defined as true. And ft::is_callable_builtin<Function>::value is being true. But Function is boost::factory<int*> and doesn't look like a callable-builtin. If I force CBI to false, then it works. Any help would be appreciated, -- Felipe Magno de Almeida