diff --git a/README.md b/README.md
index d002e24..4ad7054 100644
--- a/README.md
+++ b/README.md
@@ -35,28 +35,20 @@ RuCaptcha.configure do
   # self.style = :colorful
   # Custom captcha code expire time if you need, default: 2 minutes
   # self.expires_in = 120
-  # [Requirement/重要]
+  # [Requirement / 重要]
   # Store Captcha code where, this config more like Rails config.cache_store
   # default: Read config info from `Rails.application.config.cache_store`
   # But RuCaptcha requirements cache_store not in [:null_store, :memory_store, :file_store]
-  # 默认：会从 Rails 配置的 cache_store 里面读取相同的配置信息，用于存储验证码字符
+  # 默认：会从 Rails 配置的 cache_store 里面读取相同的配置信息，并尝试用可以运行的方式，用于存储验证码字符
   # 但如果是 [:null_store, :memory_store, :file_store] 之类的，你可以通过下面的配置项单独给 RuCaptcha 配置 cache_store
   self.cache_store = :mem_cache_store
 end
 ```
 
-Edit `config/routes.rb`, add the following code:
-
-```rb
-Rails.application.routes.draw do
-  ...
-  mount RuCaptcha::Engine => "/rucaptcha"
-  ...
-end
-```
-
 Controller `app/controller/account_controller.rb`
 
+When you called `verify_rucaptcha?`, it will uses value from `params[:_rucaptcha]` to validation.
+
 ```rb
 class AccountController < ApplicationController
   def create
@@ -68,6 +60,17 @@ class AccountController < ApplicationController
     end
   end
 end
+
+class ForgotPasswordController < ApplicationController
+  def create
+    # without any args
+    if verify_rucaptcha?
+      to_send_email
+    else
+      redirect_to '/forgot-password', alert: 'Invalid captcha code.'
+    end
+  end
+end
 ```
 
 > TIP: Sometime you may need keep last verified captcha code in session on `verify_rucaptcha?` method call, you can use `keep_session: true`. For example: `verify_rucaptcha? @user, keep_session: true`.
@@ -75,13 +78,17 @@ end
 View `app/views/account/new.html.erb`
 
 ```erb
-<form>
+<form method="POST">
   ...
   <div class="form-group">
     <%= rucaptcha_input_tag(class: 'form-control', placeholder: 'Input Captcha') %>
     <%= rucaptcha_image_tag(alt: 'Captcha') %>
   </div>
   ...
+
+  <div class="form-group">
+    <button type="submit" class="btn btn-primary">Submit</button>
+  </div>
 </form>
 ```
 
diff --git a/lib/rucaptcha.rb b/lib/rucaptcha.rb
index 98d0bfd..380f1a5 100644
--- a/lib/rucaptcha.rb
+++ b/lib/rucaptcha.rb
@@ -19,8 +19,9 @@ module RuCaptcha
       if Rails.application
         @config.cache_store = Rails.application.config.cache_store
       else
-        @config.cache_store = :null_store
+        @config.cache_store = :mem_cache_store
       end
+      @config.cache_store
       @config
     end
 
@@ -32,6 +33,27 @@ module RuCaptcha
       style = config.style == :colorful ? 1 : 0
       self.create(style)
     end
+
+    def check_cache_store!
+      cache_store = RuCaptcha.config.cache_store
+      store_name = cache_store.is_a?(Array) ? cache_store.first : cache_store
+      if [:memory_store, :null_store, :file_store].include?(store_name)
+        RuCaptcha.config.cache_store = [:file_store, Rails.root.join('tmp/cache/rucaptcha/session')]
+
+        puts "
+
+  RuCaptcha's cache_store requirements are stored across processes and machines,
+  such as :mem_cache_store, :redis_store, or other distributed storage.
+  But your current set is #{cache_store}, it has changed to :file_store for working.
+  NOTE: :file_store is still not a good way, it only works with single server case.
+
+  Please make config file `config/initializes/rucaptcha.rb` to setup `cache_store`.
+  More infomation please read GitHub RuCaptcha README file.
+  https://github.com/huacnlee/rucaptcha
+
+"
+      end
+    end
   end
 end
 
diff --git a/lib/rucaptcha/engine.rb b/lib/rucaptcha/engine.rb
index e4ff30f..1041af3 100644
--- a/lib/rucaptcha/engine.rb
+++ b/lib/rucaptcha/engine.rb
@@ -2,26 +2,14 @@ module RuCaptcha
   class Engine < ::Rails::Engine
     isolate_namespace RuCaptcha
 
-    initializer 'rucaptcha.prepend.cache' do
-      cache_store = RuCaptcha.config.cache_store
-      store_name = cache_store.is_a?(Array) ? cache_store.first : cache_store
-      if [:memory_store, :null_store, :file_store].include?(store_name)
-        msg = "
-
-  RuCaptcha's cache_store requirements are stored across processes and machines,
-  such as :mem_cache_store, :redis_store, or other distributed storage.
-  But your current set is :#{store_name}.
-
-  Please make config file `config/initializes/rucaptcha.rb` to setup `cache_store`.
-  More infomation please read GitHub RuCaptcha README file.
-
-"
-        if store_name == :null_store
-          raise msg
-        else
-          puts msg
-        end
+    initializer 'rucaptcha.init' do |app|
+      # https://github.com/rails/rails/blob/3-2-stable/actionpack/lib/action_dispatch/routing/route_set.rb#L268
+      # `app.routes.append` start from Rails 3.2 - 5.0
+      app.routes.append do
+        mount RuCaptcha::Engine => '/rucaptcha'
       end
+
+      RuCaptcha.check_cache_store!
     end
   end
 end