What steps will reproduce the problem?
1. compress with Zopfli
2. run DeflOpt on its output... it's sometimes further compressed


What is the expected output?
Zopfli is supposed to produce the smallest Deflate stream

What do you see instead?
It's not the case since DeflOpt can still reduce Zopfli output

What version of the product are you using?
Current source

On what operating system?
Linux

On enwik8:

***                 DeflOpt V2.07                 ***
***       Built on Wed Sep  5 18:56:30 2007       ***
***  Copyright (C) 2003-2007 by Ben Jos Walbeehm  ***

"Z:/home/caveman/zopfli/enwik8.gz"
Number of bytes saved: 1,745 (34,995,756 --> 34,994,011) (13,960 bits)
File rewritten.

Number of files processed  :        1
Number of files rewritten  :        1
Total number of bytes saved:    1,745


DeflOpt is avaible here:
http://www.walbeehm.com/download/
It can be run on Linux using Wine.

Defluff is a similar tool:
http://encode.ru/threads/1214-defluff-a-deflate-huffman-optimizer

If you need a tool to compare Deflate streams, defdb can be downloaded from 
here:
http://encode.ru/threads/1428-defdb-a-tool-to-dump-the-deflate-stream-from-gz-an
d-png-files