AWS WaF Rules for JSON body

Is there anyway to change the AWS WAF rules to treat the body of requests as JSON rather than simply a string. I am getting a number of False positives, caused by data being posted and the quotes in the JON being treated as user input. As on the service I am processing JSON it is safe to not flag the request.

Creating rules manually in AWS WAF allows you to set the body type as JSON (and then only evaluate, keys, values or keys and values.