[boost] [thread] Problem with thread test 'failed to write output file'

Attempting to run the 'thread' tests locally I get: failed to write output file '..\..\..\bin.v2\libs\thread\test\upg_lock_cons_move_ctor_sh_lock_untl_p_lib.test\msvc-12.0\debug\threading-multi\sync\mutual_exclusion\locks\upgrade_lock\cons\move_ctor_shared_lock_until_pass.obj.rsp'! This is with the --abbreviated-path option. If I try using --hash or not using either on the b2 command line I still get the same result of 'failed to write output file ... etc,' probably because the output file spec is still too long. This happens on Windows thread tests with msvc-12.0 but not with gcc-4.9.2. Any ideas how I can get this to run successfully ?