Version 1.3.1 has breaking changes (as well as 1.3.0)

[kapso]

class Blog < ApplicationRecord
  extend Mobility

  translates :title, dirty: true
end


blog = Blob.new
blog.title

(irb):5:in `<main>': undefined method `[]' for nil (NoMethodError)

          translations[locale.to_s]
                      ^^^^^^^^^^^^^

The above issue does not happen in 1.2.9

Config

Mobility.configure do
  plugins do
    backend :jsonb
    active_record

    reader
    writer

    cache

    dirty
    presence
  end
end

[shioyama]

Did you read the release notes for 1.3.0? It says right there: there are breaking changes. This is not a bug.