'Zoolander 2' -- Blue Steel Meets Justin Bieber

Are we in for another walk-off?

"Zoolander 2" is shaping up to be the king of cameos ... as Ben Stiller just revealed Justin Bieber will make an appearance in the flick.

Bieber has hinted he might be appearing, writing, "Working on something big right now in Europe. To learn more follow me on Fahlo. He is so hot right now."

The photo kind of lets the cat out of the bag.

No word on what Biebs will do in the cameo ... maybe he's a graduate of "The Derek Zoolander Center For Kids Who Can't Read Good And Wanna Learn To Do Other Stuff Good Too."