Traceback with Zope 2.7.4 and Version 1.1.9

I am trying to run DirectoryStorage over the PVFS2 filesystem. I'm
getting the following traceback from version 1.1.9:

Traceback (most recent call last):
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/run.py", line 50, in ?
    run()
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/run.py", line 19, in run
    start_zope(opts.configroot)
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/__init__.py", line 51,
in start_zope
    starter.startZope()
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/__init__.py", line 230,
in startZope
    Zope.startup()
  File "/srv/zope-2.7.4/lib/python/Zope/__init__.py", line 47, in
startup
    _startup()
  File "/srv/zope-2.7.4/lib/python/Zope/App/startup.py", line 57, in
startup
    DB = configuration.dbtab.getDatabase('/', is_root=1)
  File "/srv/zope-2.7.4/lib/python/DBTab/DBTab.py", line 96, in
getDatabase
    db = self._createDatabase(name, is_root)
  File "/srv/zope-2.7.4/lib/python/DBTab/DBTab.py", line 113, in
_createDatabase
    db = factory.open()
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/datatypes.py", line 172,
in open
    DB = self.createDB()
  File "/srv/zope-2.7.4/lib/python/Zope/Startup/datatypes.py", line 169,
in createDB
    return ZODBDatabase.open(self)
  File "/srv/zope-2.7.4/lib/python/ZODB/config.py", line 97, in open
    return ZODB.DB(section.storage.open(),
  File "/srv/zope-2.7.4/lib/python/DirectoryStorage/config.py", line 6,
in open
    from DirectoryStorage.Filesystem import Filesystem
  File "/srv/zope-2.7.4/lib/python/DirectoryStorage/Filesystem.py", line
9, in ?
    from PosixFilesystem import PosixFilesystem as Filesystem
  File "/srv/zope-2.7.4/lib/python/DirectoryStorage/PosixFilesystem.py",
line 19, in ?
    from readdir import opendir
ImportError: No module named readdir

I already compiled readdir so I do not understand why this is happening.
Am I missing a python module?