This is hard to teach, hard to remember, and error prone: script: b2 -j3 libs/beast/test toolset=clang cxxstd=11 cxxflags=-stdlib=libc++ linkflags=-stdlib=libc++ There's an issue to address it in a straightforward fashion: https://github.com/boostorg/build/issues/287 Anyone know how to do this and have the will to make life easier for poor overworked library maintainers? Regards