The models: class User has_many :institution_memberships belongs_to :account
after_create :set_default_membership def set_default_membership if institution_memberships.empty? institution_memberships.create(default_data_from_account) end end end class InstitutionMembership validates_uniqueness_of :user_id, :scope => :institution_id end Controller: def create @account = Account.new @account.transaction do @user = User.new(params[:user]) @institution = Institution.new(:name => @account.name) @user.account = @account @institution.account = @account @institution_membership = InstitutionMembership.new( :institution => @institution, :user => @user ) if @user.save && @institution.save && @institution_membership.save end end end To put this into context. A user can belong to one or many institutions. The relationship is managed through :institution_memberships. A user can only have one membership per institution, hence the validates_uniqueness_of :user_id, :scope => :institution_id There is a lot more code happening around all of this than i've shown, but the main problem is that basically two memberships are being created for a user with the same institution. The validate is not working. The after_create callback is creating an object successfully, and the standard save in the controller is working. My guess is it has something to do with the timing of things and when they're actually written to the database, but i don't know that process well enough to pinpoint the exact cause. Obviously there is no need to create a membership object in the controller, but the code had been that way for a long time without a problem. Nobody noticed it until suddenly the bad data started showing up. I'm more curious as to why the validation goes through. What's the community think? -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscr...@googlegroups.com. To post to this group, send email to rubyonrails-talk@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rubyonrails-talk/a290ade05152fbdef11416ed80fab3b3%40ruby-forum.com. For more options, visit https://groups.google.com/groups/opt_out.