__file__ value is lost when using different ScriptEngine instances in the same thread (v2.7.4b1)

[hinerm]

Hello,

When I run this code:

ScriptEngineManager mgr = new ScriptEngineManager();
final String script = "print __file__\n";
for (int i=0; i<5; i++) {
	ScriptEngine pyEngine = mgr.getEngineByName("jython");
	pyEngine.put(ScriptEngine.FILENAME, "hello" + i +".py");
	pyEngine.eval(script);
}

On any execution after the first I get errors with __file__ being undefined. This does not happen if I use a single ScriptEngine instance, or if each instance runs in a separate thread.

I can see that the interpreter gets the __file__ value appropriately, but then it is lost here.

Is there a contract that would explain this behavior or is it a bug?