Weird artifacts along top side of screen when splitting

[BasketaksSjargong]

Picture included.
Whenever i spawn windows I get this weird artifact bar along the top side. I have a gap size of 16 set. I have tried with other sizes.
Splitting vertically gives me even worse artifacts.

[BasketaksSjargong]

Adding

for_window [class="^.*"] border pixel 1

to .i3/config fixes the problem! :)

[rojr]

Also:
new_window 1pixel