Dialyzer and raise exception behavior

Background

I have a very minimalistic function that can return a boolean or blow up:

defmodule TestDialzer do

  @spec hello(integer) :: boolean
  def hello(n) do

    if n == 10 do
      true
    else
      raise "This is not a number!"
    end

  end
end

As you can see, this function can return a boolean. But it can also not return one. Dialyzer is not picking this up:

Starting Dialyzer
[
  check_plt: false,
  init_plt: '/home/pedro/Workplace/test_dialzer/_build/dev/dialyxir_erlang-23.3_elixir-1.12.0_deps-dev.plt',
  files: ['/home/pedro/Workplace/test_dialzer/_build/dev/lib/test_dialzer/ebin/Elixir.TestDialzer.beam'],
  warnings: [:unknown]
]
Total errors: 0, Skipped: 0, Unnecessary Skips: 0
done in 0m0.77s
done (passed successfully)

My spec is incomplete and I expected dialyzer to fail with some kind of error / warning.

Questions

Why is dialyzer not complaining? (rare thing to ask, I know)