Progress! I got things to build again, and I've been able to reproduce the failure. I was using this as a project-jam file: import option ; using msvc : 15.9 : : <cxxflags>-DBOOST_NO_ANSI_APIS <cxxflags>-DBOOST_USE_WINAPI_VERSION=0x0A00 <cxxflags>-DBOOST_USE_WINDOWS_H=1 <cxxflags>-D_WIN32_WINNT=0x0A00 <cxxflags>-D_MT <cxxflags>-D_WIN32 <cxxflags>-DNOMINMAX <cxxflags>-DWIN32_LEAN_AND_MEAN ; option.set keep-going : false ; This gives the reported failures, but which is, as far as I can see, correct, and I've used this pjf before. Now I did what Peter said and I've used: using msvc : : : ; no more, that works. There is one weird error "not recognizing //" but it's on std::cerr apparently [only on the console], so it's hard to see where this happened as the rest goes to std::cout [and is logged to file]. So telling b2 it's Win10 gives this failure, donnu. degski -- *“If something cannot go on forever, it will stop" - Herbert Stein*