diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -122,6 +122,9 @@ coreconfigitem('format', 'manifestcaches
 coreconfigitem('format', 'maxchainlen',
     default=None,
 )
+coreconfigitem('format', 'obsstore-version',
+    default=None,
+)
 coreconfigitem('hostsecurity', 'ciphers',
     default=None,
 )
diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
--- a/mercurial/obsolete.py
+++ b/mercurial/obsolete.py
@@ -717,7 +717,7 @@ def makestore(ui, repo):
     """Create an obsstore instance from a repo."""
     # read default format for new obsstore.
     # developer config: format.obsstore-version
-    defaultformat = ui.configint('format', 'obsstore-version', None)
+    defaultformat = ui.configint('format', 'obsstore-version')
     # rely on obsstore class default when possible.
     kwargs = {}
     if defaultformat is not None: