When trying to add css to the spree admin, i'm adding a new test.css file to vendor/assets/stylesheets/spree/backed directory - which should add styles to the admin area.

When I add any code at all to the new css file, the admin styles disapear.

// vendor/assets/stylesheets/spree/backed/test.css
 h2{color: red} 

The rails console now shows this error:

ActionController::RoutingError (No route matches [GET] "/assets/spree/backend/all-deed0b7192c0c311a733984b9a43b3a1ef9daab896dfac19ea2f36590ec6ddf9.css"):