PILのzlibサポートが機能しない

Debianの指示に従ってPILをインストールしようとしていますが、この部分を修正する方法がわかりません。

build_ext から --- ZLIB(PNG/ZIP) サポートを受けました。*セルフテスト中にZLIB（PNG / ZIP）サポートがインストールされない

私は何を見逃していますか？

root@portman:~/dist/Imaging-1.1.7# python setup.py build_ext -i
running build_ext
--------------------------------------------------------------------
PIL 1.1.7 SETUP SUMMARY
--------------------------------------------------------------------
version       1.1.7
platform      linux2 2.7.2+ (default, Dec  1 2011, 01:55:02)
              [GCC 4.6.2]
--------------------------------------------------------------------
*** TKINTER support not available
--- JPEG support available
--- ZLIB (PNG/ZIP) support available
--- FREETYPE2 support available
--- LITTLECMS support available
--------------------------------------------------------------------
To add a missing option, make sure you have the required
library, and set the corresponding ROOT variable in the
setup.py script.

To check the build, run the selftest.py script.
root@portman:~/dist/Imaging-1.1.7# python selftest.py
--------------------------------------------------------------------
PIL 1.1.7 TEST SUMMARY
--------------------------------------------------------------------
Python modules loaded from ./PIL
Binary modules loaded from ./PIL
--------------------------------------------------------------------
--- PIL CORE support ok
*** TKINTER support not installed
--- JPEG support ok
*** ZLIB (PNG/ZIP) support not installed
--- FREETYPE2 support ok
--- LITTLECMS support ok
--------------------------------------------------------------------
Running selftest:
--- 57 tests passed.