For reasons I can't understand, large numbers (almost all actually) of the Math lib tests have just started failing on both master and develop, the error messages all relate to missing object files, for example from a PCH build like this: http://www.boost.org/development/tests/master/developer/output/teeks99-02j-w... LINK : fatal error LNK1181: cannot open input file 'C:\local\teeks99-02\j\results\boost\bin.v2\libs\math\test\msvc-12.0\debug\asynch-exceptions-on\link-static\threading-multi\pch_light.obj' Or from common object files that are built with an "obj" rule: http://www.boost.org/development/tests/master/developer/teeks99-02j-win2008-... LINK : fatal error LNK1181: cannot open input file 'C:\local\teeks99-02\j\results\boost\bin.v2\libs\math\test\msvc-12.0\debug\asynch-exceptions-on\link-static\threading-multi\compile_test_main.obj' I'm unable to reproduce locally (at least when building in libs/math/test), and strangely not all test runners are showing the issue - though most of them are. Anyone any ideas? Thanks, John.