Full-size image smushed

Hi,

in WP Smush Pro settings I have "Smush my original full-size images -- not"

If I upload large photo like 4800x3600, full-size image is not smushed.

But if I upload small photo like 150x150, full-size image is smushed. So I lost my original uploaded image!

How to fix it?

Thanks,
Jiri