How to set default image in paperclip ruby on rails

Recently I installed Paperclip gem and I am struggling to make the default image work on my system, I put the image file inside `assets/images/pic.png`. This is code in my model `User`: ``` has_attached_file :pic, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :default_url => 'missing_:avatar.png' #:default_url => 'assets/images/avatar.png' has_attached_file :attach ``` This is code inside my `AddPicPaperClip` migration: ``` def self.up add_column :users, :pic_file_name, :string add_column :users, :pic_content_type, :string add_column :users, :pic_file_size, :integer add_column :users, :pic_updated_at, :datetime add_attachment :users, :pic end def self.down remove_column :users, :pic_file_name remove_column :users, :pic_content_type remove_column :users, :pic_file_size remove_column :users, :pic_updated_at remove_attachment :users, :pic end ``` In order to display the image in my show I have this code: ``` <%= image_tag @user.pic.url(:medium) %> ``` Could you help me find a solution, in order to show a default picture before a user inputs his own profile picture?