I've just added Membership 2 protection to an Appointments+ page and I'm getting this erro

Warning: Missing argument 3 for App_Membership2::get_price() in /home/content/86/10957786/html/wp-content/plugins/appointments/includes/class_app_membership2.php on line 89

The "no payment required" box is ticked for the appointments+ setting. The error obviously goes away if I deactivate Membership 2.

Suggestions much appreciated!