How to bypass to_param - Rails

I have this in my post model

class Post < ActiveRecord::Base
  has_many :tags
  has_many :comments
  before_validation :generate_permalink
  validates :permalink, uniqueness: true
  validates :title, presence: true
  validates :description, presence: true


  def generate_permalink
    self.permalink = title.parameterize
  end

  def to_param
    permalink
  end

end

and i use this model for both posts controller(admin) and posts controller(blog).

Now due to the nature of this setup, i have problems displaying errors if validations fail on the title (you can read more here: Ruby on Rails won't render edit page without id)

is there a way to easily bypass to_param method for certain controllers and/or actions?