Adding new action to devise registrations_controller

my main devise route is:

devise_for :accounts,  :controllers => { :registrations => "users/accounts/registrations", :sessions => "accounts/devise/sessions" }, :class_name => 'Admin' 

Then I want a new url/action so i add the following BEFORE the devise_for line above:

match '/accounts/signedup/' => 'users/accounts/registrations#signedup':

then in the controller i have the signedup action, but when i go to myurl.com/accounts/signedup which currently just has:

def signedup
    Rails.logger.debug { "&& signed_up" }
end

Then I go to myurl.com/accounts/signedup I get:

AbstractController::ActionNotFound (AbstractController::ActionNotFound):

But if I remove the def signedup from the controller I instead get:

The action 'signedup' could not be found for Users::Accounts::RegistrationsController"

Any idea what's wrong?