--- a/mercurial/localrepo.py	Sun Jul 02 13:24:23 2017 +0900
+++ b/mercurial/localrepo.py	Fri Jun 23 13:49:34 2017 +0200
@@ -442,6 +442,9 @@
             'aggressivemergedeltas', False)
         self.svfs.options['aggressivemergedeltas'] = aggressivemergedeltas
         self.svfs.options['lazydeltabase'] = not scmutil.gddeltaconfig(self.ui)
+        chainspan = self.ui.configbytes('experimental', 'maxdeltachainspan', -1)
+        if 0 <= chainspan:
+            self.svfs.options['maxdeltachainspan'] = chainspan
 
         for r in self.requirements:
             if r.startswith('exp-compression-'):