Rails 5＆Devise：最小密码长度不起作用

我正在使用Rails 5＆Devise和初始化器/ devise.rb：

config.password_length = 6..128 

注册/ new.html.erb：

   {:class => "col s12 form-text", autocomplete: "off"}, validate: true) do |f| %>  "validate", :placeholder => "Robin Smith", :required => true %>  "validate", :required => true, placeholder: " " %>  "validate", :required => true, placeholder: " " %>  "waves-effect waves-light btn-flat", :value => "Join Now" %>  

和路线：

 resources :users devise_for :users, path: '', path_names: { sign_up: 'register', sign_in: 'login', sign_out: 'logout'} 

User.rb：

 class User  true validates_format_of :email,:with => Devise::email_regexp 

由于某种原因，用户仍然可以设置0-5个字符的密码。