Front axle slides out

The front axle on my 07 Outlander 650 Max XT just slides out. If I grab the shaft and pull it towards the rear of the bike it will side right out. Is that normal? I’m getting a chattering sounds when I accelerate slowly that I think is related the this but maybe it’s normal? Should there be something holding the shaft in so that it doesn’t just do this? The u-joint seems okay.

Thanks

Dave