diff --git a/modules/nixos/services/home-assistant/default.nix b/modules/nixos/services/home-assistant/default.nix
index 16da12a..30e21cf 100644
--- a/modules/nixos/services/home-assistant/default.nix
+++ b/modules/nixos/services/home-assistant/default.nix
@@ -134,6 +134,10 @@ in
       # HA does its own mDNS discovery on the host network.
       networking.firewall.allowedUDPPorts = [ 5353 ];
 
+      # The stick ships with Zigbee firmware, so reflashing it is a prerequisite
+      # for thread mode rather than a rescue tool.
+      environment.systemPackages = [ pkgs.python3Packages.universal-silabs-flasher ];
+
       services.udev.extraRules = lib.mkIf cfg.radio.udevRule ''
         SUBSYSTEM=="tty", ATTRS{idVendor}=="303a", ATTRS{idProduct}=="831a", ENV{ID_USB_INTERFACE_NUM}=="00", SYMLINK+="${lib.removePrefix "/dev/" cfg.radio.device}", GROUP="dialout", MODE="0660"
       '';