Error with sshkit 1.8.1

[micred]

I got error on colorized log used by acme_wrapper in this gem:

cap aborted!
NoMethodError: undefined method `light_black' for "2016-03-11 14:59:59 +0100":String
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/letsencrypt-cli-0.2.0/lib/letsencrypt/cli/acme_wrapper.rb:16:in `block (2 levels) in log'
/Users/michele/.rvm/rubies/ruby-2.2.2/lib/ruby/2.2.0/logger.rb:491:in `call'
/Users/michele/.rvm/rubies/ruby-2.2.2/lib/ruby/2.2.0/logger.rb:491:in `format_message'
/Users/michele/.rvm/rubies/ruby-2.2.2/lib/ruby/2.2.0/logger.rb:379:in `add'
/Users/michele/.rvm/rubies/ruby-2.2.2/lib/ruby/2.2.0/logger.rb:434:in `info'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/letsencrypt-cli-0.2.0/lib/letsencrypt/cli/acme_wrapper.rb:19:in `log'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/capistrano-lets-encrypt-0.2.0/lib/capistrano/tasks/lets-encrypt.rake:58:in `check_certificate'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/capistrano-lets-encrypt-0.2.0/lib/capistrano/tasks/lets-encrypt.rake:32:in `block (3 levels) in <top (required)>'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/sshkit-1.8.1/lib/sshkit/backends/abstract.rb:15:in `instance_exec'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/sshkit-1.8.1/lib/sshkit/backends/abstract.rb:15:in `run'
/Users/michele/.rvm/gems/ruby-2.2.2@rails5/gems/sshkit-1.8.1/lib/sshkit/runners/parallel.rb:13:in `block (2 levels) in execute'
Tasks: TOP => lets_encrypt:authorize

I solved locking sshkit to 1.7.1:

gem 'sshkit', '1.7.1'