X-Powered-By header set by Azure Traffic Manager

I am having trouble removing the X-Powered-By: ARR/2.5 header which is being set by the Azure Traffic Manager.

I have the following architecture:

Web VM (IIS/8.5) -> Routing VM (ARR/2.5 IIS/8.5) -> Azure Traffic Manager -> Custom Domain Name.

• When I make a HTTP request to my Web VM there are no X-Powered-By headers
• When I make a HTTP request to my Routing VM there are no X-Powered-By headers
• When I make a HTTP request to my traffic manager, i.e. http://my_app.trafficmanager.net then theX-Powered-By: ARR/2.5 header appears.

Is this a known issue within Azure Traffic Manager?