How can I append a path to my PATH with home-manager for new shells using home.sessionPath without needing reboot?

home = {
  sessionPath = [

This seems to work when restarting, but not when launching new shells.

I see that it ends up in .profile

$cat .profile
. "/home/b0ef/.nix-profile/etc/profile.d/"

…and that contains

$ cat .nix-profile/etc/profile.d/
# Only source this once.
if [ -n "$__HM_SESS_VARS_SOURCED" ]; then return; fi

export PATH="$PATH${PATH:+:}/home/b0ef/.foo/bar"

, but I want it to append my PATH for new shells, not needing to reboot.