Meetup Invalid Authorization request

Trying to connect to Meetup.com API using OAuth2.0 I had a problem which I find out this is not documented in their API documentation.
The redirect_url parameter is case sensitive. So if this is the case then you will recieve the error message :

Invalid Authorization request

If you were directed here by another application, contact its developer

So make sure that the redirect uri of your application defined at http://www.meetup.com/meetup_api/oauth_consumers/ exactly(case wise) matches the redirect_uri parameter you pass in your authorization request.