diff --git a/CHANGELOG.md b/CHANGELOG.md
index 571ac19..8364a72 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+0.5.0
+
+- Fix cache with Rails 5.
+
 0.4.5
 -----
 
diff --git a/Gemfile b/Gemfile
index 46a4f91..8a579c5 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,4 +1,8 @@
 source 'https://rubygems.org'
 
 gemspec
+
+gem 'rake'
+gem 'rails'
+gem 'rspec'
 gem 'mini_magick'
diff --git a/Gemfile.lock b/Gemfile.lock
index 5edd2d6..c86999a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    rucaptcha (0.4.5)
+    rucaptcha (0.5.0)
 
 GEM
   remote: https://rubygems.org/
@@ -127,7 +127,7 @@ DEPENDENCIES
   mini_magick
   rails
   rake
-  rspec (>= 3.3.0)
+  rspec
   rucaptcha!
 
 BUNDLED WITH
diff --git a/lib/rucaptcha.rb b/lib/rucaptcha.rb
index 14cc0a7..d1a8b43 100644
--- a/lib/rucaptcha.rb
+++ b/lib/rucaptcha.rb
@@ -25,11 +25,6 @@ module RuCaptcha
 
     def configure(&block)
       config.instance_exec(&block)
-
-      # enable cache if cache_limit less than 1
-      if config.cache_limit >= 1
-        RuCaptcha::Captcha.send(:include, RuCaptcha::Cache)
-      end
     end
   end
 end
diff --git a/lib/rucaptcha/cache.rb b/lib/rucaptcha/cache.rb
index 35bc482..7e7ceaa 100644
--- a/lib/rucaptcha/cache.rb
+++ b/lib/rucaptcha/cache.rb
@@ -3,30 +3,27 @@ require 'fileutils'
 module RuCaptcha
   # File Cache
   module Cache
-    extend ActiveSupport::Concern
-
-    included do
-      class << self
-        alias_method_chain :create, :cache
-        alias_method_chain :random_chars, :cache
+    def self.prepended(base)
+      class << base
+        prepend ClassMethods
       end
     end
 
     module ClassMethods
-      def create_with_cache(code)
-        cache.fetch(code) do
-          create_without_cache(code)
+      def create(code)
+        cache.fetch(code, expires_in: 1.days) do
+          super(code)
         end
       end
 
-      def random_chars_with_cache
+      def random_chars
         if cached_codes.length >= RuCaptcha.config.cache_limit
           return cached_codes.sample
-        else
-          code = random_chars_without_cache
-          cached_codes << code
-          return code
         end
+
+        code = super
+        cached_codes << code
+        code
       end
 
       def cache
@@ -35,7 +32,8 @@ module RuCaptcha
         cache_path = Rails.root.join('tmp', 'cache', 'rucaptcha')
         FileUtils.mkdir_p(cache_path) unless File.exist? cache_path
         @cache = ActiveSupport::Cache::FileStore.new(cache_path)
-        @cache.clear
+        # clear expired captcha cache files on Process restart
+        @cache.cleanup
         @cache
       end
 
diff --git a/lib/rucaptcha/captcha.rb b/lib/rucaptcha/captcha.rb
index eda910c..8952f65 100644
--- a/lib/rucaptcha/captcha.rb
+++ b/lib/rucaptcha/captcha.rb
@@ -77,7 +77,7 @@ module RuCaptcha
           png_file_path
         else
           command.strip!
-          out, err, st = Open3.capture3(command)
+          out, err, _st = Open3.capture3(command)
           raise "RuCaptcha: #{err.strip}" if err.present?
           out
         end
diff --git a/lib/rucaptcha/engine.rb b/lib/rucaptcha/engine.rb
index a31f704..2e8d2af 100644
--- a/lib/rucaptcha/engine.rb
+++ b/lib/rucaptcha/engine.rb
@@ -1,5 +1,12 @@
 module RuCaptcha
   class Engine < ::Rails::Engine
     isolate_namespace RuCaptcha
+
+    initializer 'rucaptcha.prepend.cache' do
+      # enable cache if cache_limit less than 1
+      if RuCaptcha.config.cache_limit >= 1
+        RuCaptcha::Captcha.send(:prepend, RuCaptcha::Cache)
+      end
+    end
   end
 end
diff --git a/lib/rucaptcha/version.rb b/lib/rucaptcha/version.rb
index 983bde2..ef06ee8 100644
--- a/lib/rucaptcha/version.rb
+++ b/lib/rucaptcha/version.rb
@@ -1,3 +1,3 @@
 module RuCaptcha
-  VERSION = '0.4.5'
+  VERSION = '0.5.0'
 end
diff --git a/rucaptcha.gemspec b/rucaptcha.gemspec
index c672f27..228fa28 100644
--- a/rucaptcha.gemspec
+++ b/rucaptcha.gemspec
@@ -1,20 +1,15 @@
 lib = File.expand_path('../lib/', __FILE__)
-$:.unshift lib unless $:.include?(lib)
+$LOAD_PATH.unshift lib unless $LOAD_PATH.include?(lib)
 
-require "rucaptcha/version"
+require 'rucaptcha/version'
 
 Gem::Specification.new do |s|
-  s.name = 'rucaptcha'
-  s.version = RuCaptcha::VERSION
-  s.authors = ['Jason Lee']
-  s.email = 'huacnlee@gmail.com'
-  s.files        = Dir.glob("lib/**/*") + Dir.glob("app/**/*") + Dir.glob("config/**/*") + %w(README.md CHANGELOG.md)
-  s.homepage = 'https://github.com/huacnlee/rucaptcha'
+  s.name          = 'rucaptcha'
+  s.version       = RuCaptcha::VERSION
+  s.authors       = ['Jason Lee']
+  s.email         = 'huacnlee@gmail.com'
+  s.files         = Dir.glob('lib/**/*') + Dir.glob('app/**/*') + Dir.glob('config/**/*') + %w(README.md CHANGELOG.md)
+  s.homepage      = 'https://github.com/huacnlee/rucaptcha'
   s.require_paths = ['lib']
-  s.summary = 'This is a Captcha gem for Rails Application. It run ImageMagick command to draw Captcha image.'
-
-
-  s.add_development_dependency 'rake'
-  s.add_development_dependency 'rails'
-  s.add_development_dependency 'rspec', '>= 3.3.0'
+  s.summary       = 'This is a Captcha gem for Rails Application. It run ImageMagick command to draw Captcha image.'
 end
diff --git a/spec/cache_spec.rb b/spec/cache_spec.rb
index 4cab649..0656403 100644
--- a/spec/cache_spec.rb
+++ b/spec/cache_spec.rb
@@ -5,17 +5,17 @@ describe RuCaptcha::Cache do
     it 'should generate max chars by config.cache_limit' do
       allow(RuCaptcha.config).to receive(:cache_limit).and_return(5)
       items = []
-      10.times do
-        items << RuCaptcha::Captcha.random_chars_with_cache
+      100.times do
+        items << RuCaptcha::Captcha.random_chars
       end
-      expect(items.uniq.length).to eq 5
+      expect(items.uniq.length).to eq RuCaptcha.config.cache_limit
       expect(RuCaptcha::Captcha.cached_codes).to eq items.uniq
     end
   end
 
   describe '.create' do
     it 'should work' do
-      expect(RuCaptcha::Captcha).to receive(:create_without_cache).and_return('aabb')
+      expect(RuCaptcha::Captcha).to receive(:create).and_return('aabb')
       expect(RuCaptcha::Captcha.create('abcd')).to eq('aabb')
     end
   end
diff --git a/spec/captcha_spec.rb b/spec/captcha_spec.rb
index 4e55dc3..f2412a8 100644
--- a/spec/captcha_spec.rb
+++ b/spec/captcha_spec.rb
@@ -3,16 +3,16 @@ require 'spec_helper'
 describe RuCaptcha::Captcha do
   describe '.random_chars' do
     it 'should len equal config.len' do
-      expect(RuCaptcha::Captcha.random_chars_without_cache.length).to eq(RuCaptcha.config.len)
+      expect(RuCaptcha::Captcha.random_chars.length).to eq(RuCaptcha.config.len)
     end
 
     it 'should return 0-9 and lower str' do
-      expect(RuCaptcha::Captcha.random_chars_without_cache).to match(/[a-z0-9]/)
+      expect(RuCaptcha::Captcha.random_chars).to match(/[a-z0-9]/)
     end
 
     it 'should not include [0ol1]' do
       10_000.times do
-        expect(RuCaptcha::Captcha.random_chars_without_cache).not_to match(/[0ol1]/i)
+        expect(RuCaptcha::Captcha.random_chars).not_to match(/[0ol1]/i)
       end
     end
   end