diff --git a/mercurial/pycompat.py b/mercurial/pycompat.py
--- a/mercurial/pycompat.py
+++ b/mercurial/pycompat.py
@@ -403,7 +403,8 @@
 
 isjython = sysplatform.startswith(b'java')
 
-isdarwin = sysplatform == b'darwin'
+isdarwin = sysplatform.startswith(b'darwin')
+islinux = sysplatform.startswith(b'linux')
 isposix = osname == b'posix'
 iswindows = osname == b'nt'