I was going though the exercises in http://elixirkoans.io and stumbled upon something odd. even if my code does solve the problem i don’t get a pass.

Exercise:

koan "Be careful, a message may be altered" do
    assert String.replace("An awful day", "awful", "incredible") == String.replace("awful","awful","incredible", global: true)
  end

Console response

Be careful, a message may be altered
Assertion failed in lib/koans/02_strings.ex:23
assert(String.replace("An awful day", "awful", "incredible") == String.replace("awful", "awful", "incredible", global: true))

left:  "An incredible day"
right: "incredible"

The answers they expect can be seen here https://github.com/elixirkoans/elixir-koans/blob/master/test/koans/strings_koan_test.exs and i think is the same thing I am providing.
So why doesn’t my answer get a successful pass?

Thanks