My projects need to define WIN32_LEAN_AND_MEAN. Unfortunately, they receive many compilation warnings due to macro redefinition in the following Boost headers (1.34.1). boost/iostreams/detail/system_failure.hpp boost/spirit/iterator/impl/file_iterator.ipp I understand that I can avoid the need to define WIN32_LEAN_AND_MEAN by ensuring that Boost headers are always included prior to <windows.h>. I do not like the idea of include order dependencies, as I am certain that I will come back to bite me down the road. Another option would be to turn the particular warning off; however, I would rather not do this. Would it be prudent to patch the Boost headers to only define WIN32_LEAN_AND_MEAN if it is not already defined? If not, is there another solution that I am overlooking. Thanks, Justin