javascript - How to remove border from stacked column chart in Chartkick - Chart.js -

i using chart.js throug chartkick gem.

= column_chart [{"name":"a","data":[["2016-07-01",1],["2016-08-01",0],["2016-09-01",0]]},{"name":"b","data":[["2016-07-01",1],["2016-08-01",0],["2016-09-01",0]]}], xtitle: "date range", ytitle: "counts", stacked: true, height: "600px" 

i getting following chart:

i don't want border around stacked blocks. want set border 0. how can achieve using chartkick gem?

i tried adding on page load in application.js.

chart.defaults.global.elements.rectangle.borderwidth = 0; 

but not working.