Not quite secure images for everything (https)

Good job on launching the image proxy in August: https://blog.newsblur.com/post/187031418021/secure-images-for-everybody

I’m seeing a mixed content warning because one of the thumbnail images on my home page is coming in via http. This is the image:

http://pegasus-pulp.com/wp-content/uploads/2019/11/51SXLjNPuOL.SY346-193x300.jpg

And this is the feed:
http://corabuhlert.com/feed/

Is the intent to proxy all images including this one through your proxy?