fix failing test on erlang 18 release candidate
fix failing test on erlang 18 release candidate

pedrosnk/elixir,pedrosnk/elixir,michalmuskala/elixir,elixir-lang/elixir,kelvinst/elixir,ggcampinho/elixir,joshprice/elixir,lexmag/elixir,antipax/elixir,beedub/elixir,kimshrier/elixir,antipax/elixir,kimshrier/elixir,beedub/elixir,lexmag/elixir,gfvcastro/elixir,kelvinst/elixir,ggcampinho/elixir,gfvcastro/elixir