Ferret not working after upgrade

After a recent upgrade to a newer ferret version and acts_as_ferret
plugin, searching is not working any more.

I have changed find_by_contents to find_with_ferret, but it still doesnt
work. :frowning:

user.rb
acts_as_ferret({:fields => [‘username’, ‘lastname’, ‘town’})

search form.rhtml
<% form_tag({ :action => “search” }, :method => “get”) do %>
<%= text_field_tag “q”, params[:q] %>
<%= submit_tag “Search” %>
<% end %>

controller:
def search
if params[:q]
@users = User.find_with_ferret(params[:q])
end
end

Any help would be most welcome.
Thank you.