diff -r e8cd688b2eb1 -r 3764330f76a6 mercurial/upgrade.py
--- a/mercurial/upgrade.py	Mon Nov 12 01:22:30 2018 +0100
+++ b/mercurial/upgrade.py	Mon Nov 12 01:22:38 2018 +0100
@@ -269,7 +269,7 @@
 
     _requirement = localrepo.SPARSEREVLOG_REQUIREMENT
 
-    default = False
+    default = True
 
     description = _('in order to limit disk reading and memory usage on older '
                     'version, the span of a delta chain from its root to its '