Rails: Passing multiple parameters to form_for url?

This works great:

- form_for @user, :url => { :action => :create, :type => @type } do |f| ...

Returns /users/(id)?type=type

But in another view I need to pass TWO parameters into the URL string, and this does not work:

- form_for @user, :url => { :action => :update, :type => @type, :this => @currently_editing } do |f| ...

Returns /users/(id)?this=currently_editing

I've also tried:

- form_for @user, :url => { :action => :update, :params = params.merge({:this => @currently_editing, :type = @type})} do |f| ...

... with no luck (error: only GET requests allowed).

What I want is for it to return this: /users/(id)?this=currently_editing&type=type

Thoughts?