diff --git a/example/aitf-update-cache b/example/aitf-update-cache
index 20f40d1ce04913d8b86aacc00b03ac02d596f6b1..d71fa5d4d7658d268accb9efff9b6b60df73fa39 100755
--- a/example/aitf-update-cache
+++ b/example/aitf-update-cache
@@ -116,6 +116,8 @@ def unlink_if_old(filename, expiration_time, stats):
     expiration time is epoch time, as returned by os.path.getmtime(path) 
     or time.time().
 
+    stats is a CleaningStats object (above)
+
     If the file doesn't exist, does nothing, does not raise an exception.
     This is on the theory that another process may have cleaned it up
     while we were considering doing so.