What did you do?

Modified *.icns file inside the app on MacOS

What did you expect to happen?

Updated icon to be visible using Finder/Get Info.

What actually happened?

After upgrading Pillow to 8.3.0 version, updating *.icns file inside the application on MacOS, makes the app icon not visible/invalid in Finder, though all the icons are visible if you open the icns file directly.

What are your OS, Python and Pillow versions?

• OS: MacOS 10.15 Catalina
• Python: 3.7.7, 3.9.7
• Pillow: 8.3.0 or 8.3.1, 8.4.0

with Image.open(image_path) as image:
    draw=ImageDraw.Draw(image)
    draw.rectangle([(0,0), (image.width,image.height)], fill=(255,0,0))
    image.save(image.filename)