oga 2.16 and 2.17 are broken for Ruby 1.9.3

The AWS SDK for Ruby still supports Ruby 1.9.3 and uses the oga gem. Our CI is failing:

Failure/Error: require 'oga/xml/querying'
SyntaxError:
  /home/travis/.rvm/gems/ruby-1.9.3-p551/gems/oga-2.16/lib/oga/xml/querying.rb:43: syntax error, unexpected tLABEL
        def xpath(expression, variables = {}, namespaces: nil)
                                                         ^
  /home/travis/.rvm/gems/ruby-1.9.3-p551/gems/oga-2.16/lib/oga/xml/querying.rb:104: syntax error, unexpected keyword_end, expecting $end
  end # Oga

The spec dependency still lists 1.9.3 as supported. If necessary - could these versions be yanked and a new version pushed with proper support?