Adverts could soon be coming to a Facebook chat near you.
According to the document, the origins of which have been kept secret, businesses will be able to send adverts as messages to Facebook users who have messaged them before.
In order to prepare for the change, the document reportedly recommends that companies take steps to get people to message them now, so they can take advantage of the advertising feature once it rolls out.
Facebook has been turning its chat feature into a customer service platform for the last few years, bringing in new tweaks and buttons that make it easier for customers to contact companies over Messenger, rather than through emails or contact forms.
Speaking to TechCrunch, Facebook said it doesn't comment on rumours or speculation.
However, it did say: "Our aim with Messenger is to create a high quality, engaging experience for 800 million people around the world, and that includes ensuring people do not experience unwanted messages of any type."
Facebook is obviously already filled with adverts, but they're mostly fairly unobtrusive, usually taking the form of banners at the sides of the page or promoted posts on users' newsfeeds.
However, buzzing users' phones with adverts and filling up their Messenger inboxes would probably annoy them, so Facebook will have to deploy the new feature very carefully.