diff --git a/mercurial/pure/parsers.py b/mercurial/pure/parsers.py
--- a/mercurial/pure/parsers.py
+++ b/mercurial/pure/parsers.py
@@ -47,7 +47,7 @@
     def _fix_index(self, i):
         if not isinstance(i, int):
             raise TypeError("expecting int indexes")
-        if i < 0 or i >= len(self) + 1:
+        if i < 0 or i >= len(self):
             raise IndexError
         return i