Radar chartjs background fill not showing vue-chart

Question

I'm having this setting :

        datasets: [{
      label: 'My First dataset',
      fillColor: "rgba(217, 108, 99, .9)",
      backgroundColor: 'rgba(179,181,198,0.2)',
      borderColor: 'rgba(179,181,198,1)',
      pointBackgroundColor: 'rgba(179,181,198,1)',
      pointBorderColor: '#fff',
      pointHoverBackgroundColor: '#fff',
      pointHoverBorderColor: 'rgba(179,181,198,1)',
      data: [65, 59, 90, 81, 56, 55, 40]
    }, {
      label: 'My Second Dataset',
      data: [28, 48, 40, 19, 96, 27, 100],
      backgroundColor: 'rgba(54, 162, 235, 0.2)',
      borderColor: 'rgb(54, 162, 235)',
      pointBackgroundColor: 'rgb(54, 162, 235)',
      pointBorderColor: '#fff',
      pointHoverBackgroundColor: '#fff',
      pointHoverBorderColor: 'rgb(54, 162, 235)'
    }]
  },
  chartOptions: {
    elements: {
      line: {
        borderWidth: 3
      }
    },
    responsive: true,
    maintainAspectRatio: false
  }

which leads to this result :

I can't find a way to fill the background of those datasets.