AutoOrient and Save

[bertasoft]

var inStream = ... open image

 using (var image = Image.Load<Rgba32>(inStream))
 {
     image.Save("somepath.jpg"); //is original

     image.Mutate(x => x.AutoOrient()); //in debug i can see that the image width and height are changed

     image.Save("somepath2.jpg"); //is same like original, no rotation, save doesn't commit?
}

WHY?