Ruby syntax error after updating Logstash to 5.6.7

Elastic Stack Logstash
3

That does not work either. Logstash 5.6.7 logs

SyntaxError: (ruby filter code):7: syntax error, unexpected tRCURLY
        }
        ^
              eval at org/jruby/RubyKernel.java:1079
          register at /usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-ruby-3.1.3/lib/logstash/filters/ruby.rb:59
          register at /usr/share/logstash/vendor/jruby/lib/ruby/1.9/forwardable.rb:201
   register_plugin at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:290
  register_plugins at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:301
              each at org/jruby/RubyArray.java:1613
  register_plugins at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:301
     start_workers at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:311
               run at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:235
    start_pipeline at /usr/share/logstash/logstash-core/lib/logstash/agent.rb:408