Prevent lock screen picture from fading

Hi all,

Do you know how I can prevent the image on my lock screen from fading/shuffling in and out of existence.

I want to have one image as my regular background and a different one as my lock screen background. But when I choose the latter from my image gallery it starts shuffling through all the images in my gallery, which in my case means just shuffling the one image again and again.

Thanks for your help,