The selection filtering doesn't work

[BlobCodes]

I recently tried to use the filter option, only to find out it doesn't work at all.
I tried the following code (copied from the readme):

require "term-prompt"
prompt = Term::Prompt.new()

warriors = %w(Scorpion Kano Jax Kitana Raiden)
prompt.select("Choose your destiny?", warriors, filter: true)

..but when you type in a character, nothing gets actually filtered. It stays as-is.