I have this model:

class SuccessCriterion < ActiveRecord::Base
extend Enumerize
extend ActsAsTree::TreeWalker

enumerize :level, in: [:a, :aa, :aaa]

acts_as_tree order: :position, dependent: :restrict_with_error
acts_as_list scope: [:parent_id]
end

After upgrading from v2.5.1 to v2.6, I get this error when calling`success_criterion.level_text`:

    undefined method `text' for 0:Fixnum

Any idea where's the problem?