Replying on a tweet with Twython

[Cecil Westerhof]

I just found Twython. I managed to post a tweet with:
    from twython import Twython
    twitter = Twython(APP_KEY, APP_SECRET,
                      OAUTH_TOKEN, OAUTH_TOKEN_SECRET)
    posted = twitter.update_status(status = quote)

But I want to send a reply on this tweet. I tried:
        posted = twitter.update_status(status = follow_up, in_reply_id = posted['id_str'])

But that does not work. How could I make it work?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof