Not possible to set background color of unchanged lines

[lrustand]

It is not possible to change the background color of unchanged lines. I tried the following, which did not produce an error, but did not work either.

(set-face-background 'git-gutter:unchanged "red")

However all of these work:

(set-face-background 'git-gutter:modified "red")
(set-face-background 'git-gutter:added "red")
(set-face-background 'git-gutter:deleted "red")

[lrustand]

Also, I wish there was a way to set the background once for all of them, instead of having to specify it four times.