macOS Catalina Safari's image upload shows .heic instead of .jpeg

The photos that I take with my iPhone are synced to iCloud and to my Mac's Photos library.

Since updating to Catatalina, whenever I try to upload an image in Safari from my Mac's Photos library all the photos show up as .heic instead of .jpeg.

I am aware that iPhone, iCloud and Mac takes store them as .heic but in macOS Mojave they'd be on-the-fly converted to jpeg. That does not seem to happen anymore.

Does anyone see this too or am I facing a bug? Or is there a setting that got switched back when I did the upgrade to macOS Catalina?

As you can see in the screenshot, the image field expects png, gif, jpg or jpeg files. The .heic files in the image upload dialog are grayed out, while the .PNG ones are selectable for upload.