Highcharts 曲线上的借点不显示

（红色部分）
            plotOptions: {
                spline: {
                    lineWidth: 4,
states: {
                        hover: {
                            lineWidth: 5  
                        }
                    },
                    marker: {
                        enabled: false
//radius: 10
                    },
                    pointInterval: 3600000, // one hour
                    pointStart: Date.UTC(2009, 9, 6, 0, 0, 0)
                }
            },

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