LibGDX 3D Camera lookAt() Problem

If you've ever used the method camera lookAt() method, you may have noticed that afterwards, your view of the (virtual) world is slightly off-kilter. 

For some reason, the methods alters the camera.up value, which should ideally be (0, 1, 0).

What is the solution?  Just manually set the direction yourself like so:-

tmpVector.set(targetPosition).sub(camera.position).nor();
player.camera.direction.set(tmpVector);
player.camera.update();

I've no idea why the lookAt() method does what it does.