--- a/mercurial/configitems.py	Fri Jun 30 03:43:13 2017 +0200
+++ b/mercurial/configitems.py	Fri Jun 30 03:37:05 2017 +0200
@@ -107,6 +107,9 @@
 coreconfigitem('commands', 'update.requiredest',
     default=False,
 )
+coreconfigitem('debug', 'dirstate.delaywrite',
+    default=0,
+)
 coreconfigitem('devel', 'all-warnings',
     default=False,
 )

--- a/mercurial/dirstate.py	Fri Jun 30 03:43:13 2017 +0200
+++ b/mercurial/dirstate.py	Fri Jun 30 03:37:05 2017 +0200
@@ -766,7 +766,7 @@
 
         # enough 'delaywrite' prevents 'pack_dirstate' from dropping
         # timestamp of each entries in dirstate, because of 'now > mtime'
-        delaywrite = self._ui.configint('debug', 'dirstate.delaywrite', 0)
+        delaywrite = self._ui.configint('debug', 'dirstate.delaywrite')
         if delaywrite > 0:
             # do we have any files to delay for?
             for f, e in self._map.iteritems():