Web Audio API - Frequency Modulation is different in Chrome / Safari

I am working on a browser based patch interface for Web Audio API synthesizers. Frequency modulation (connecting an oscillator to the frequency of another oscillator) works as expected in Chrome. It should be a sci-fi sound such as a 300Hz waveform with a 30Hz frequency.

In Safari (and Mobile Safari), it just sounds like a low hum. It looks like there is FM, but not the correct base frequency. Is this just a browser quirk that will be ironed out in future versions? Is there a workaround now?

Here is a visual / interactive version:

http://forresto.github.com/dataflow-webaudio/

And a version of the script with minimal code to demonstrate the effect:
http://jsfiddle.net/FVaWL/28/

var mod, modGain, osc;

var out = context.destination;

var startTest = function(){
    mod = context.createOscillator();
    mod.frequency.value = 8;

    modGain = context.createGain();
    modGain.gain.value = 30;

    osc = context.createOscillator();
    osc.frequency.value = 300;

    mod.connect(modGain);
    modGain.connect(osc.frequency);
    osc.connect(out);

    osc.start(0);
    mod.start(0);
};

var stopTest = function(){
    osc.stop(0);
    mod.stop(0);
    mod = modGain = osc = null;
};