form_tag can't use get method

Hi there

I try to use form_tag form_tag( post_path, :method => :put)
to generate <form action='"/posts" method="get">

But I got the following code

<form action='"/posts?method=get" method="post">

I am in rails 3.0.0 beta 3

Any one have the same situation? would you like to tell me how to fix
it?

Cheers,
Danyi