Touch called on parent destroy

I have two models: Project and Tags

class Project < ActiveRecord::Base
  has_many :tags, :dependent => :destroy
end

class Tag < ActiveRecord::Base
  belongs_to :project, :touch => true
end

And every project must have at least one tag (I skipped the valiations). So when project.destroy is called, I get the following error message:

...application/vendor/rails/activerecord/lib/active_record/validations.rb:1090:in save_without_dirty!' ...application/vendor/rails/activerecord/lib/active_record/dirty.rb:87:insave_without_transactions!' ...application/vendor/rails/activerecord/lib/active_record/transactions.rb:200:in save!' ...application/vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb:136:intransaction' ...application/vendor/rails/activerecord/lib/active_record/transactions.rb:182:in transaction' ...application/vendor/rails/activerecord/lib/active_record/transactions.rb:200:insave!' ...application/vendor/rails/activerecord/lib/active_record/transactions.rb:208:in rollback_active_record_state!' ...application/vendor/rails/activerecord/lib/active_record/transactions.rb:200:insave!' ...application/vendor/rails/activerecord/lib/active_record/timestamp.rb:37:in touch' ...application/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:221:insend' ...application/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:221:in method_missing' ...application/vendor/rails/activerecord/lib/active_record/associations.rb:1380:inbelongs_to_touch_after_save_or_destroy_for_project' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:178:in send' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:178:inevaluate_method' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:166:in call' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:93:inrun' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:92:in each' ...application/vendor/rails/activesupport/lib/active_support/callbacks.rb:92:insend'

It seems that every tag.destroy call project.touch, and my guess the last touch is invalid because the project needs at least one tag. In my opinion, when the project is destroyed it shouldn't be touched at all.

Does someone know a workaround? Thanks