diff --git a/nix/os/devices/disk.nix b/nix/os/devices/disk.nix
index ff75d5b..6684521 100644
--- a/nix/os/devices/disk.nix
+++ b/nix/os/devices/disk.nix
@@ -45,7 +45,11 @@ in rec {
     [[ -e "''${NIXOS_CONFIG}" ]]
     [[ -e "${mntRootVol}/nixos" ]]
 
+    sudo -E $SHELL <<EOF
+    # 'having $system set breaks nixos-install'
+    unset system
     nixos-install --max-jobs 5 --cores 4  --no-root-passwd --root ${mntRootVol}/nixos
+    EOF
   '';
 
   diskPrepare = pkgs.writeScript "script" ''