How to set pointStyle for bubble chart dataset?

I've looked through the documentation and found this page: http://www.chartjs.org/docs/latest/charts/bubble.html#dataset-properties.

Apparently `pointStyle` is a valid dataset property, but setting it seems to have no effect. I've setup a codepen post to show what I've tried: https://codepen.io/halfpastfouram/pen/XqJpOQ.

Am I setting the property incorrectly?
