Definitely not a normal thing to do, but I accidentally copied colours from the bottom bar to the top bar like this:

[bar/top]
background = ${bar/top.background}
foreground = ${bar/top.foreground}

Definitely not urgent, as this was user-error, but segfaults are bad.

On Arch linux:

polybar 3.0.5-70-g5b7d7b8

Features: +alsa +curl +i3 +mpd +network