Remove subscriptionform.css

I am using the filter hook membership_override_registration_form in a plugin in order to use my own view for the registration (step 1 of form). But I notice that even when overriding the view I still get subscriptionform.css loaded. Is there a way to prevent this stylesheet from being loaded? I tried wp_dequeue_style('subscriptionformcss') in the add_subscription_styles filter to no avail. What should I be doing?

Thanks in advance.