[Merb] Authentication question!

Hey guys, sorry, there is no Merb subforum over here, but i have really
small question for authentication in merb, which is similar to rails.

I created my own strategy, assigned sessions to datamapper and it
works very well, no problems with that. But on another side im getting
weird parameter in url all time after loggin in.

For example:

  1. /login => success
  2. redirects to /home with ?_message=…some…data… in url

The question is: what this variable for and how to get rid of it? I
find out that this message contains encoded session data, but cant
figure out why it goes there

Any suggestions?