--- a/mercurial/revlog.py	Wed Aug 04 13:21:11 2010 -0500
+++ b/mercurial/revlog.py	Fri Aug 06 12:59:13 2010 -0500
@@ -1041,6 +1041,9 @@
             base = self._cache[1]
             text = self._cache[2]
 
+        # drop cache to save memory
+        self._cache = None
+
         self._loadindex(base, rev + 1)
         self._chunkraw(base, rev)
         if text is None: