diff --git a/chartjs/chart-tests.ts b/chartjs/chart-tests.ts
index 2374b6228a..4bd8820c6c 100644
--- a/chartjs/chart-tests.ts
+++ b/chartjs/chart-tests.ts
@@ -252,12 +252,12 @@ var myPolarAreaChart = new Chart(ctx).PolarArea(polarAreaData, {
 
 var myPolarAreaChartLegend: string = myPolarAreaChart.generateLegend();
 var myPolarAreaChartImage: string = myPolarAreaChart.toBase64Image();
-myPolarAreaChart.addData([{
+myPolarAreaChart.addData({
     value: 120,
     color: "#4D5360",
     highlight: "#616774",
     label: "Dark Grey"
-}], 0);
+}, 0);
 myPolarAreaChart.clear();
 myPolarAreaChart.removeData(0);
 myPolarAreaChart.resize();
@@ -301,12 +301,12 @@ var myPieChart = new Chart(ctx).Pie(pieData, {
 
 var myPieChartLegend: string = myPieChart.generateLegend();
 var myPieChartImage: string = myPieChart.toBase64Image();
-myPieChart.addData([{
+myPieChart.addData({
     value: 120,
     color: "#4D5360",
     highlight: "#616774",
     label: "Dark Grey"
-}], 0);
+}, 0);
 myPieChart.clear();
 myPieChart.removeData(0);
 myPieChart.resize();
@@ -329,12 +329,12 @@ var myDoughnutChart = new Chart(ctx).Doughnut(pieData, {
 
 var myDoughnutChartLegend: string = myDoughnutChart.generateLegend();
 var myDoughnutChartImage: string = myDoughnutChart.toBase64Image();
-myPieChart.addData([{
+myPieChart.addData({
     value: 120,
     color: "#4D5360",
     highlight: "#616774",
     label: "Dark Grey"
-}], 0);
+}, 0);
 myDoughnutChart.clear();
 myDoughnutChart.removeData(0);
 myDoughnutChart.resize();
diff --git a/chartjs/chart.d.ts b/chartjs/chart.d.ts
index d85f9b4760..9da7245f61 100644
--- a/chartjs/chart.d.ts
+++ b/chartjs/chart.d.ts
@@ -113,7 +113,7 @@ interface LinearInstance extends ChartInstance {
 interface CircularInstance extends ChartInstance {
     getSegmentsAtEvent: (event: Event) => {}[];
     update: () => void;
-    addData: (valuesArray: CircularChartData[], index: number) => void;
+    addData: (valuesArray: CircularChartData, index?: number) => void;
     removeData: (index: number) => void;
     segments: Array<CircularChartData>;
 }