5 Beta install java.lang.reflect.InaccessibleObjectException error

Elastic Stack Logstash
1

Bah:

Java HotSpot(TM) 64-Bit Server VM warning: Option UseParNewGC was deprecated in version 9.0 and will likely be removed in a future release.
LoadError: load error: jruby/java/java_ext/java.lang -- java.lang.reflect.InaccessibleObjectException: Cannot make a non-public member of class java.lang.reflect.AccessibleObject accessible
  require at org/jruby/RubyKernel.java:1040
   (root) at file:/usr/share/logstash/vendor/jruby/lib/jruby.jar!/jruby/java/java_ext.rb:3
  require at org/jruby/RubyKernel.java:1040
   (root) at file:/usr/share/logstash/vendor/jruby/lib/jruby.jar!/jruby/java.rb:1
Unable to install system startup script for Logstash.

Anyone seen this one before?

2

Java version:

java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+134)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+134, mixed mode)
3

Looks like java 9 isn't supported yet: https://github.com/elastic/logstash/issues/5985, though the docs say "or later" https://www.elastic.co/guide/en/logstash/5.0/installing-logstash.html