diff -r 75979c8d4572 -r 238abf65a8ad mercurial/worker.py
--- a/mercurial/worker.py	Thu Oct 12 23:30:46 2017 -0700
+++ b/mercurial/worker.py	Thu Oct 12 09:04:22 2017 -0700
@@ -53,7 +53,7 @@
             raise error.Abort(_('number of cpus must be an integer'))
     return min(max(countcpus(), 4), 32)
 
-if pycompat.osname == 'posix':
+if pycompat.isposix:
     _startupcost = 0.01
 else:
     _startupcost = 1e30