accepts_nested_attributes_for with belongs_to polymorphic

I would like set up a polymorphic relation with accepts_nested_attributes_for. Here is the code:

class Contact <ActiveRecord::Base
  has_many :jobs, :as=>:client
end

class Job <ActiveRecord::Base
  belongs_to :client, :polymorphic=>:true
  accepts_nested_attributes_for :client
end

When I try to access Job.create(..., :client_attributes=>{...} gives me NameError: uninitialized constant Job::Client