I just updated to the latest develop. I ran bootstrap, then nuked my boost directory and reran b2 headers. Worked fine. Then I changed directory to libs/proto/test and ran ../../../b2 mem_ptr to run a test. Here's what I get: f:\modular-boost\libs\proto\test>..\..\..\b2 mem_ptr Performing configuration checks - symlinks supported : no - junctions supported : yes - hardlinks supported : yes ...patience... ...patience... ...found 4951 targets... ...updating 441 targets... common.mkdir ..\..\..\bin.v2\libs common.mkdir ..\..\..\bin.v2\libs\proto common.mkdir ..\..\..\bin.v2\libs\proto\test common.mkdir ..\..\..\bin.v2\libs\proto\test\mem_ptr.test common.mkdir ..\..\..\bin.v2\libs\proto\test\mem_ptr.test\msvc-12.0 common.mkdir ..\..\..\bin.v2\libs\proto\test\mem_ptr.test\msvc-12.0\debug common.mkdir ..\..\..\bin.v2\libs\proto\test\mem_ptr.test\msvc-12.0\debug\link-static common.mkdir ..\..\..\bin.v2\libs\proto\test\mem_ptr.test\msvc-12.0\debug\link-static\threading-multi link.rm ..\..\..\boost\mpl common.mkdir ..\..\..\boost\mpl link.hardlink ..\..\..\boost\mpl\print.hpp Hardlink created for ..\..\..\boost\mpl\print.hpp <<===>> ..\..\mpl\include\boost\mpl\print.hpp <snip> link.rm ..\..\..\boost\numeric\conversion link.hardlink ..\..\..\boost\numeric\conversion\conversion_traits.hpp The system cannot find the path specified. if exist "..\..\..\boost\numeric\conversion\conversion_traits.hpp" del "..\..\..\boost\numeric\conversion\conversion _traits.hpp" mklink /H "..\..\..\boost\numeric\conversion\conversion_traits.hpp" "..\..\numeric\conversion\include\boost\numeric\ conversion\conversion_traits.hpp" ...failed link.hardlink ..\..\..\boost\numeric\conversion\conversion_traits.hpp... link.hardlink ..\..\..\boost\numeric\conversion\int_float_mixture_enum.hpp The system cannot find the path specified. For some reason, b2 thinks it needs to rerun b2 headers, but it does a crap job of it and dies. What's going on? Eric