[Plasma+i3] applications called from i3 exec do not load desktop theme

Something weird happens on NixOS when trying to call a program using i3’s exec function bound to a key combination (e.g. opening Konsole using Meta+Enter). It opens the application successfully but it does not load the desktop theme (colors/fonts/etc). Opening the application using a menu, the launcher, or calling the command directly works as expected. The issue only happens when I call them using the i3 exec function, and only on NixOS. I have tried the exact same setup in my Arch and Gentoo installations and the problem is absent there. Maybe it’s related to how i3 invokes the shell an how NixOS handles its location?

See the below screenshots for reference. Side by side, how i3 exec opens applications and how they open normally.

It’s a really minor issue; I can work around it by disabling the i3 shortcut and enabling the same one within Plasma, but still it’s something that shouldn’t happen.