ScriptEngineManager().getEngineByName("jruby") returns NULL

ScriptEngineManager().getEngineByName("jruby") returns NULL

I am trying to use JRuby in Java and I keep getting a null returned when I
do:
ScriptEngine blah = new ScriptEngineManager().getEngineByName("jruby")
returns NULL
I've looked at any material I can find but nothing seems to get me any
further then I have so far. Plus alot of the materials are 5+ years old.
I'm sure the classpaths are correct and I've done the setup correct.
Please help.