Custom toolbar icons (20x20) only display 16x16 pixels

I have a .ICO file that contains only one image and it's 20x20, but when I use it (or any other of my custom icons) as the icon for a toolbar button, it only displays as 16x16.
Attached is an example -- the icon on the left is a built-in Opus icon, the one on the right is my icon. The zip is my .ICO file.
Red_X_on_black__icon.zip (429 Bytes)

Turn off the Scale Toolbar button images option in Preferences -> Display -> Toolbars.

Thanks, but it didn't change anything.

When you convert your .ico file to .png, it seems to work ...
Red X on black.zip (554 Bytes)

Super awesome coolness. Thank you.