Logstash-output-lumberjack plugin not packaged with logstash 5.1?

[inigo]

According to the documentation, the lumberjack output plugin should be available with Logstash 5.1, however I'm seeing the following error when trying to use it:

[2017-01-20T14:47:27,608][ERROR][logstash.plugins.registry] Problems loading a plugin with {:type=>"output", :name=>"lumberjack", :path=>"logstash/outputs/lumberjack", :error_message=>"NameError", :error_class=>NameError, :error_backtrace=>["/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:221:in namespace_lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:157:in legacy_lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:133:in lookup'", "/usr/share/logstash/logstash-core/lib/logstash/plugins/registry.rb:175:in lookup_pipeline_plugin'", "/usr/share/logstash/logstash-core/lib/logstash/plugin.rb:127:in lookup'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:447:in plugin'", "(eval):164:in initialize'", "org/jruby/RubyKernel.java:1079:in eval'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:93:in initialize'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:237:in create_pipeline'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:94:in register_pipeline'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:259:in execute'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:67:in run'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:178:in run'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:132:in run'", "/usr/share/logstash/lib/bootstrap/environment.rb:71:in (root)'"]}:

I can see logstash-input-lumberjack is still there:

[logstash]$ bin/logstash-plugin list logstash-input-lumberjack
logstash-input-lumberjack

Is there a reason why the logstash-output-lumberjack isn't?

[logstash]$ bin/logstash-plugin list logstash-output-lumberjack
ERROR: No plugins found