Vagrant: rake db:seed_fu ENV=development fails

Seeding the database during vagrant up --provision fails with

== Seed from /home/git/gitlab/db/fixtures/development/07_milestones.rb
rake aborted!
undefined method `id' for nil:NilClass
/home/git/gitlab/.bundle/ruby/2.0.0/gems/seed-fu-2.3.0/lib/seed-fu/runner.rb:46:in `eval'
/home/git/gitlab/app/services/event_create_service.rb:38:in `open_milestone'
/home/git/gitlab/app/observers/milestone_observer.rb:3:in `after_create'
....