Unexplainable Dialyzer warning

dialyzer_test.ex

defmodule DialyzerTest do
  def call(map) when is_map(map) do
    with :ok <- validate_1(map[:value_1]),
         :ok <- validate_2(map[:value_2]) do
      :ok
    else
      {:error, reason} ->
        # lib/dialyzer_test.ex:10:exact_eq
        # The test :bad_value_2 == :bad_value_1 can never evaluate to 'true'.
        if !map[:required] && reason == :bad_value_1 do
          :ok
        else
          {:error, reason}
        end
    end
  end

  defp validate_1(true), do: :ok
  defp validate_1(_), do: {:error, :bad_value_1}

  defp validate_2(true), do: :ok
  defp validate_2(_), do: {:error, :bad_value_2}
end