Preserve case in ConfigParser?

I have tried to use Python's ConfigParser module to save settings. For my app it's important that I preserve the case of each name in my sections. The docs mention that passing str() to ConfigParser.optionxform() would accomplish this, but it doesn't work for me. The names are all lowercase. Am I missing something?

<~/.myrc contents>
[rules]
Monkey = foo
Ferret = baz

Python pseudocode of what I get:

import ConfigParser,os

def get_config():
   config = ConfigParser.ConfigParser()
   config.optionxform(str())
    try:
        config.read(os.path.expanduser('~/.myrc'))
        return config
    except Exception, e:
        log.error(e)

c = get_config()  
print c.options('rules')
[('monkey', 'foo'), ('ferret', 'baz')]