Flows HTTP Post (mailchimp) using form with checkbox

I have a form for email signups that will be sent to mailchimp.
I’m using Flows to set up the HTTP post request.
Its all working great for the text fields but I’m having a problem with the interests field. Mailchimp is expecting boolean values. I’m populating from a form checkbox (and so that is boolean). It looks like it may be sent as ‘True’ or something?

Mailchimp documentation: https://mailchimp.com/developer/marketing/api/list-members/add-member-to-list/

My project: Webflow - LivableHawaiiKaiHui
In the project, it is the Email Signup page.

Any ideas on how to fix the flow so the checkbox value will look like a boolean in the JSON?
If this is documented somewhere, just point me in the right direction.