     case state.includes[arg] do
       nil ->
         warn "There is no includable named `#{arg}'."
-        ""
-      stub when is_binary(stub) -> stub
+        nil
+      stub -> stub
     end
   end
 

        |> Stream.filter(&String.ends_with?(&1, ".html.eex"))
        |> Stream.map(&String.replace_suffix(&1, ".html.eex", ""))
        |> Stream.map(&do_load_includes(&1, state))
        |> Enum.map(&render_includes(&1, state))
        |> Error.filter_results_with_values(:load_includes)
      case result do
        {:ok, list} -> {:ok, Map.put(state, :includes, Map.new(list))}

      {:error, reason} -> {:error, {reason, path, 0}}
      {:ct_error, msg, line} -> {:error, {msg, path, line}}
    end
  end

  @doc """
