diff -r 1d5d7e2b7ab5 -r 03608e8d09e9 mercurial/exchange.py
--- a/mercurial/exchange.py	Sat Jun 17 13:17:10 2017 +0200
+++ b/mercurial/exchange.py	Sat Jun 17 13:25:42 2017 +0200
@@ -1980,7 +1980,7 @@
         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)