NotImplementedError: pbkdf2_hmac() function is unimplemented on this machine

I am working on upgrading ruby and rails version to my app. I was using rails 3.2, and ruby '1.9.3', For this version Gibberish works fine on heroku. After I upgraded rails 4.2 and ruby 2.2.0, Gibberish not working and through an error on heroku.

So I created a new app in heroku and configured 4.2 and 2.2.0 and then tested. There Gibberish works fine without any error. But I don't like to configured new app. Because I have well configured on my existing app. Is there any point did I missed? Here the trace...

irb(main):002:0> Gibberish::AES.new("12345").encrypt("data")
NotImplementedError: pbkdf2_hmac() function is unimplemented on this machine
from /app/vendor/bundle/ruby/2.2.0/gems/gibberish-2.0.0/lib/gibberish/aes.rb:140:in `pbkdf2_hmac'
from /app/vendor/bundle/ruby/2.2.0/gems/gibberish-2.0.0/lib/gibberish/aes.rb:140:in `encrypt'
from /app/vendor/bundle/ruby/2.2.0/gems/gibberish-2.0.0/lib/gibberish/aes.rb:100:in `encrypt'
from (irb):2
from /app/vendor/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/commands/console.rb:110:in `start'
from /app/vendor/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/commands/console.rb:9:in `start'
from /app/vendor/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:68:in `console'
from /app/vendor/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /app/vendor/bundle/ruby/2.2.0/gems/railties-4.2.0/lib/rails/commands.rb:17:in `<top (required)>'
from bin/rails:10:in `require'
from bin/rails:10:in `<main>'

Note: I am working latest version on Gibberish

Thanks in advance!