[boost] [variant] Bug in recursive_wrapper_fwd.hpp?

I've been tracking down an preprocessor warning involving the redefinition of BOOST_TT_AUX_BOOL_TRAIT_DEF1. It appears to me, in boost 1.33.0, that recursive_wrapper_fwd.hpp is misusing: #include "boost/type_traits/detail/bool_trait_def.hpp" The usual include pattern for this header is: // should be the last #include #include "boost/type_traits/detail/bool_trait_def.hpp" ... #include "boost/type_traits/detail/bool_trait_undef.hpp" But recursive_wrapper_fwd.hpp has: #include "boost/type_traits/detail/bool_trait_def.hpp" #include "boost/mpl/aux_/lambda_support.hpp" ... and no include for bool_trait_undef.hpp. Is that as intended? Thanks, Howard