As of the moment, the BOOST_MSVC_ENABLE_2014_JUN_CTP macro must be defined to eliminate a bunch of macros that should not apply to the Visual Studio 2015 Preview: BOOST_NO_CXX11_ALIGNAS [no value] BOOST_NO_CXX11_CHAR16_T [no value] BOOST_NO_CXX11_CHAR32_T [no value] BOOST_NO_CXX11_INLINE_NAMESPACES [no value] BOOST_NO_CXX11_NOEXCEPT [no value] BOOST_NO_CXX11_REF_QUALIFIERS [no value] BOOST_NO_CXX11_UNICODE_LITERALS [no value] BOOST_NO_CXX11_USER_DEFINED_LITERALS [no value] In other words, the only CXX11 macros that should be defined are: BOOST_NO_CXX11_ADDRESSOF [no value] BOOST_NO_CXX11_CONSTEXPR [no value] Unless someone objects strongly in the next few hours, I'm going to remove the need for the BOOST_MSVC_ENABLE_2014_JUN_CTP macro; it is just causing confusion at this point. --Beman