diff -r e8cd688b2eb1 -r 3764330f76a6 mercurial/configitems.py
--- a/mercurial/configitems.py	Mon Nov 12 01:22:30 2018 +0100
+++ b/mercurial/configitems.py	Mon Nov 12 01:22:38 2018 +0100
@@ -694,7 +694,7 @@
     default=None,
 )
 coreconfigitem('format', 'sparse-revlog',
-    default=False,
+    default=True,
 )
 coreconfigitem('format', 'usefncache',
     default=True,