diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -17,7 +17,7 @@ from . import (
 
 def loadconfigtable(ui, extname, configtable):
     """update config item known to the ui with the extension ones"""
-    for section, items in configtable.items():
+    for section, items in sorted(configtable.items()):
         knownitems = ui._knownconfig.setdefault(section, itemregister())
         knownkeys = set(knownitems)
         newkeys = set(items)