       }
       {:callback, writeme, current}
     else
-      GenServer.reply(current.from, current.reply)
+      GenServer.reply(current.from, current.reply || "R02")
       nil
     end
   end

  @spec handle_busy(current) :: current
  defp handle_busy(current) do
    debug_log "refreshing timer."
    Process.cancel_timer(current.timer)
    timer = Process.send_after(self(), :timeout, @default_timeout_ms)
    %{current | status: :busy, timer: timer}
  end

  @spec handle_locked(current, Context.t) :: :locked
  defp handle_locked(current, ctx) do
    if current do
      true = Process.cancel_timer(current.timer)
    end
    # Side effects.
    Farmbot.BotState.lock_bot(ctx)
