Shoulda-matchers validation error

email.rb

class Email < ActiveRecord::Base

  scope :by_account, -> account_id { where(account_id: account_id) }

  attr_accessible :template_name, :subject, :content, :user_id, :account_id

  validates  :subject,       presence: true
  validates  :template_name, presence: true
  validates  :template_name, uniqueness: { :scope => :account_id }
  validates  :content,       presence: true

  has_many   :links,         dependent: :destroy
  belongs_to :account
  belongs_to :user

end

email__spec.rb

require 'spec_helper'

describe Email do
  
  describe "Validations" do

    context "when created with invalid attributes" do

      it "will not be created without :subject" do
        should validate_presence_of(:subject)
      end

      it "will not be created without :template_name" do
        should validate_presence_of(:template_name)
      end

      it "will not be created without :content" do
        should validate_presence_of(:content)
      end

      it "does not allow emails with duplicate template_name for a account" do
        should validate_uniqueness_of(:template_name).scoped_to(:account_id)
      end
    
    end
  
  end

end

shoulda-matchers validation error

Failures:

  1) Email Validations when created with invalid attributes does not allow emails with duplicate template_name for a account
     Failure/Error: should validate_uniqueness_of(:template_name).scoped_to(:account_id)
     ActiveRecord::StatementInvalid:
       PG::Error: ERROR:  null value in column "subject" violates not-null constraint
       : INSERT INTO "emails" ("account_id", "archive", "as_web_page", "attachment_url", "bcc", "cc", "contact_id", "content", "created_at", "current_tab", "from", "latest_activity_date", "status", "subject", "template_name", "updated_at", "user_id") VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17) RETURNING "id"
     # ./spec/models/email_spec.rb:30:in `block (4 levels) in <top (required)>'

Finished in 5.44 seconds
135 examples, 1 failure, 2 pending

Failed examples:

rspec ./spec/models/email_spec.rb:29 # Email Validations when created with invalid attributes does not allow emails with duplicate template_name for a account

Randomized with seed 45615

Hey, I'm having the same issue with the shoulda-matchers. Have you found any solution or workaround to that problem, yet?