Can't get AWS SNS to work with Workflows

Has anyone had any luck creating an AWS SNS topic and sending notifications to Workflows? In AWS, I've created a HTTPS subscription for a SNS topic and used my Workflow's webhook URL as the endpoint.

Apparently AWS sends a POST request to the endpoint with headers and a JSON body that needs to be parsed. The POST request is hitting the workflow but I'm not seeing any data coming through, and startTrigger.headers are undefined and startTrigger.metadata is empty.