Some test suites, for example Pool and Units, use '<warnings-as-errors>on' in their project requirements, to test for a warning-free compilation. Pool, f.ex. has project : requrements <toolset>gcc:<warnings-as-errors>on <toolset>msvc:<warnings-as-errors>on ; (among others.) This, however, is propagated to dependencies, so that in [ run test_threading.cpp : : : <threading>multi <library>/boost/thread//boost_thread ] Boost.Thread is also built with '<warnings-as-errors>on', which fails. (In addition, some other tests also fail because of warnings.) So I tried to use '<warnings-as-errors>off' only for some tests, but I was unable to come up with a syntax that worked. Putting -<toolset>msvc:<warnings-as-errors>on in the test requirements didn't (no effect). <toolset>msvc:<warnings-as-errors>off didn't (conflict). -<warnings-as-errors>on didn't (no effect). -<warnings-as-errors>on <warnings-as-errors>off didn't (no effect). Is there a way to override the project requirements from the run rule?