Doesn't work in Rails 4.2 - cannot load such file -- active_support/duration/iso8601_serializer

[Nowaker]

As per the gemspec, Rails 4.2 is supported:

spec.add_dependency "activesupport", [">= 4.2", "< 5.3"]

However, it can't work:

	 4: from /Users/nowaker/.rvm/gems/ruby-2.6.3/gems/activesupport-duration-human_string-0.1.1/lib/active_support/duration/human_string.rb:2:in `<top (required)>'
	 3: from /Users/nowaker/.rvm/gems/ruby-2.6.3/gems/activesupport-4.2.11.1/lib/active_support/dependencies.rb:274:in `require'
	 2: from /Users/nowaker/.rvm/gems/ruby-2.6.3/gems/activesupport-4.2.11.1/lib/active_support/dependencies.rb:240:in `load_dependency'
	 1: from /Users/nowaker/.rvm/gems/ruby-2.6.3/gems/activesupport-4.2.11.1/lib/active_support/dependencies.rb:274:in `block in require'
/Users/nowaker/.rvm/gems/ruby-2.6.3/gems/activesupport-4.2.11.1/lib/active_support/dependencies.rb:274:in `require': cannot load such file -- active_support/duration/iso8601_serializer (LoadError)

As per https://apidock.com/rails/ActiveSupport/Duration/ISO8601Serializer, this class was introduced in Rails 5.