Problem with button_to_remote on 2.3.2

I have a link_to_remote call which works as expected:
    <%= link_to_remote "-", { :url =>
{ :action => :remove_from_cart, :id => cart_item.product} }, { :href =>
url_for(:action => :remove_from_cart, :id => cart_item.product) } %>

'Where is the button problem?