diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -39,6 +39,9 @@ def coreconfigitem(*args, **kwargs):
 coreconfigitem('patch', 'fuzz',
     default=2,
 )
+coreconfigitem('ui', 'clonebundleprefers',
+    default=[],
+)
 coreconfigitem('ui', 'quiet',
     default=False,
 )
diff --git a/mercurial/exchange.py b/mercurial/exchange.py
--- a/mercurial/exchange.py
+++ b/mercurial/exchange.py
@@ -1980,7 +1980,7 @@ class clonebundleentry(object):
         return self._cmp(other) != 0
 
 def sortclonebundleentries(ui, entries):
-    prefers = ui.configlist('ui', 'clonebundleprefers', default=[])
+    prefers = ui.configlist('ui', 'clonebundleprefers')
     if not prefers:
         return list(entries)