Apple Watch 2 Factor Authentification

I have changed my MacBook Air, the iMac and a iPhone 6S to 2 Factor Authentification. in iCloud Settings i can see my Devices. When i click on my Apple Watch, it says: "This device can not be used to obtain an Apple ID code". See (german) Screenshot: http://i64.tinypic.com/2450q6h.png Is it possible to add an Apple Watch to 2 Factor Authentification? Tweak