FactoryGirl does not work

[chrhsmt]

I develop rails app using redshift, but rspec using FactoryGirl does not work.

FactoryGirl.define do
  factory :access_log, class: AccessLog do
    datetime { Time.now }
    .....
  end
end

RSpec.describe 'Controller', type: :request do
  let!(:access_log) { FactoryGirl.create(:access_log) }
  describe 'GET /' do
    it do
      get "/", params, headers
      .......
    end
  end
end

bundle exec rspec ./spec/request/....rb

     Failure/Error: let!(:access_log) { FactoryGirl.create(:access_log) }
     NoMethodError:
       undefined method `has_precision?' for #<ActiveRecord::ConnectionAdapters::Redshift::OID::DateTime:0x007ff491cce150>

what is has_precision ? It seems to not to be defined.