JRuby 1.6.1- const_missing error depending on factory.getEngineByName("jruby")

I ran into an interesting problem when upgrading JRuby from 1.5.2 to 1.6.1. It was creeping me out all weekend until I boiled it down to a handful of lines. It seems that a bug may have been introduced somewhere that causes a failure when getEngineByName is called a few too many times. For instance, the following super-simple code works in 1.5.2 but fails in 1.6.1 after roughly 10-20 iterations:

    ScriptEngineManager factory = new ScriptEngineManager();
    for (int i = 0; i < 10000; i++) {
        System.out.println(i);
        ScriptEngine engine = factory.getEngineByName("jruby");
        engine.eval("puts 'hello'");
    }

Result in 1.6.1 after #16:

NameError: uninitialized constant #<Class:0x101a41cc7>::ARGV
  const_missing at org/jruby/RubyModule.java:2526
Exception in thread "main" java.lang.NullPointerException
    at org.jruby.embed.jsr223.JRubyEngine.wrapException(JRubyEngine.java:110)
    at org.jruby.embed.jsr223.JRubyEngine.eval(JRubyEngine.java:93)
    at org.jruby.embed.jsr223.JRubyEngine.eval(JRubyEngine.java:154)
    at JRubyTestFailure.main(JRubyTestFailure.java:16)

To avoid the problem, all you need to do is move the getEngineByName up outside the loop:

    ScriptEngineManager factory = new ScriptEngineManager();
    ScriptEngine engine = factory.getEngineByName("jruby");
    for (int i = 0; i < 10000; i++) {
        System.out.println(i);
        engine.eval("puts 'hello'");
    }

Unfortunately this is not so easy for my application, for architectural reasons. I may have to put separate ScriptEngine instances in a ThreadLocal. Not understanding why this is failin开发者_C百科g worries me though.

Any ideas on why I'm getting this "NameError: uninitialized constant" error from? Nope I haven't tried checking out the source yet...