--- a/mercurial/revlog.py	Fri Feb 05 18:23:01 2010 +0100
+++ b/mercurial/revlog.py	Fri Feb 05 19:10:26 2010 +0100
@@ -431,8 +431,8 @@
         self.index = []
 
         v = REVLOG_DEFAULT_VERSION
-        if hasattr(opener, "defversion"):
-            v = opener.defversion
+        if hasattr(opener, 'options') and 'defversion' in opener.options:
+            v = opener.options['defversion']
             if v & REVLOGNG:
                 v |= REVLOGNGINLINEDATA