jQuery UI datepicker classes Option not overwriting default classes

Question

As per the classes option guide here, I tried to overwrite the default classes used by jQuery ui datepicker.

The datepicker doesn't have a .prototype, like the other widgets, so $.ui.datepicker.prototype is undefined.

I've tried to specify classes option for each .datepicker instance like so:

$('.datepicker_selector').datepicker({ 
    classes: { "ui-datepicker": "custom_class_name" },
...

but with no success.

I've opened a ticket at the jQuery ui git repo, I'm wondering if anyone has solved this? (The datepicker works fine, no errors in console either).

Thank you for your feedback!