{{current_message}} in custom body is not working, please help!

I get the below error if I try to run current_message in custom body in a webhook call.

Error while processing request. Error Code: TemplateEngine - 0105. Server response with: An error occured during the expansion of template with key 'body'. >>Undefined context path 'current_message'. (error code: 'TemplateEngine - 0106', id: 'dc18daa0-a2f3-4f35-ae24-3e268fbfd54b')<<

Any help is great!