Why does transparency seem to get replaced with black in img2img? How to fix?

I’ve been having a go at using Stable Diffusion through Easy Diffusion. I made a png with alpha for img2img, but the transparency seems to be getting replaced with black, ruining the image. I was expecting the transparency to get replaced with noise. Are there any good fixes/workarounds?

• I don’t really want to add my own noise to the input image itself, because wouldn’t that make the randomness produced by stable diffusion useless?
• Could I manually script it to automatically layer the image over the noise, or over the image after a few steps in?
• I don’t have a dedicated graphics card yet, so I’m CPU only.