diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -11,8 +11,9 @@ from demandload import demandload
 demandload(globals(), "os time util")
 
 class changelog(revlog):
-    def __init__(self, opener):
-        revlog.__init__(self, opener, "00changelog.i", "00changelog.d")
+    def __init__(self, opener, defversion=0):
+        revlog.__init__(self, opener, "00changelog.i", "00changelog.d",
+                        defversion)
 
     def extract(self, text):
         if not text: