BCrypt Issue

bcrypt_issue.rb

#!/usr/bin/env ruby

require "uri"
require "bcrypt"

secret = "abcd/1234"
encrypted_password = BCrypt::Password.create(secret)

encoded_secret = URI.encode_www_form_component(secret)
password = URI.decode(encoded_secret)

# Interacting with `password` at all affects it.
# In Devise a presence check is performed.
# A `puts` will also cause a breakage.
puts password

bcrypt = BCrypt::Password.new(encrypted_password)

# Devise adds pepper to the password before hashing it
# this pepper can be nil and this results in a corrupt string when it gets to
# the mri layer which BCrypt uses.
password_with_nil = BCrypt::Engine.hash_secret("#{password}#{nil}", bcrypt.salt)
if password_with_nil == encrypted_password
  puts "Password with nil was correct"
else
  puts "Password with nil was incorrect"
end

password = BCrypt::Engine.hash_secret(password, bcrypt.salt)
if password == encrypted_password
  puts "Password was correct"
else
  puts "Password was incorrect"
end

Gemfile

source "https://rubygems.org"

gem "bcrypt"

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    bcrypt (3.1.9)

PLATFORMS
  ruby

DEPENDENCIES
  bcrypt

Commenting out line 15 of bcrypt_issue.rb results in both hashes passing.
This is with Ruby 2.2.0.