StackView adding extra space around one element


I have a stack view with an imageView and a couple of labels in it. The stack view is pinned 16pt all around inside the main view and the Distribution is set to Fill Proportionally.

I’m pulling data from NASA’s APOD, then populating the labels and the image (content mode: Aspect Fit). For some reason I can’t seem to get rid of the extra space around the image, whatever I set the stack view to fill proportionally or just fill, there’s always a little extra space there.

What is happening?
Is this happening because the image is set after the stack view is rendered since the web request takes a while?

Interface builder screenshot

distribution: fill proportionally

distribution: fill