diff --git a/hgext/win32text.py b/hgext/win32text.py
--- a/hgext/win32text.py
+++ b/hgext/win32text.py
@@ -139,7 +139,7 @@ def forbidnewline(ui, repo, hooktype, no
     # changegroup that contains an unacceptable commit followed later
     # by a commit that fixes the problem.
     tip = repo['tip']
-    for rev in xrange(len(repo) - 1, repo[node].rev() - 1, -1):
+    for rev in xrange(repo.changelog.tiprev(), repo[node].rev() - 1, -1):
         c = repo[rev]
         for f in c.files():
             if f in seen or f not in tip or f not in c: