Rspec & FactoryGirl acceptance validation

I've been breaking my head on this easy validation and I can't get it to validate. I've got the following model:

class Attendance < ActiveRecord::Base
  belongs_to :user, counter_cache: true
  belongs_to :event, counter_cache: true

  validates :terms_of_service, :acceptance => true
end

This is my Factory:

  factory :attendance do
    user
    event
    terms_of_service true
  end

This is my test:

  describe "event has many attendances" do
    it "should have attendances" do
      event = FactoryGirl.create(:event)
      user1 = FactoryGirl.create(:user, firstname: "user1", email: "mail@user2.nl")
      user2 = FactoryGirl.create(:user, firstname: "user2", email: "mail@user1.nl")

      attendance1 = FactoryGirl.create(:attendance, event: event, user: user1, terms_of_service: true)    
    end
  end

This shouldn't bring up any errors but it does.

Running spec/models/workshop_spec.rb
.............F

Failures:

  1) Event event has many attendances should have attendances
     Failure/Error: attendance1 = FactoryGirl.create(:attendance, event: event, user: user1, terms_of_service: true)
     ActiveRecord::RecordInvalid:
       Validation failed: Terms of service must be accepted
     # ./spec/models/event_spec.rb:33:in `block (3 levels) in <top (required)>'

When i do these actions in my browser and i accept the tos all goes well. What am i missing here?!