diff -r 6952d42f9158 -r d1d919f679f7 contrib/automation/hgautomation/cli.py
--- a/contrib/automation/hgautomation/cli.py	Sun Sep 29 11:24:14 2019 -0700
+++ b/contrib/automation/hgautomation/cli.py	Sun Sep 29 11:29:25 2019 -0700
@@ -352,7 +352,7 @@
         '--distro',
         help='Linux distribution to run tests on',
         choices=linux.DISTROS,
-        default='debian9',
+        default='debian10',
     )
     sp.add_argument(
         '--filesystem',