diff --git a/src/core/echarts.ts b/src/core/echarts.ts
index 8214c11e0e..3c60b2362d 100644
--- a/src/core/echarts.ts
+++ b/src/core/echarts.ts
@@ -1023,6 +1023,9 @@ class ECharts extends Eventful<ECEventDefinition> {
             return;
         }
 
+        // `opts` is optional, as the `opts && ...` reads below and `getDataURL` assume.
+        opts = opts || {};
+
         const isSvg = opts.type === 'svg';
         const groupId = this.group;
         const mathMin = Math.min;
diff --git a/test/ut/spec/api/getConnectedDataURL.test.ts b/test/ut/spec/api/getConnectedDataURL.test.ts
new file mode 100644
index 0000000000..748a22a71e
--- /dev/null
+++ b/test/ut/spec/api/getConnectedDataURL.test.ts
@@ -0,0 +1,60 @@
+/*
+* Licensed to the Apache Software Foundation (ASF) under one
+* or more contributor license agreements.  See the NOTICE file
+* distributed with this work for additional information
+* regarding copyright ownership.  The ASF licenses this file
+* to you under the Apache License, Version 2.0 (the
+* "License"); you may not use this file except in compliance
+* with the License.  You may obtain a copy of the License at
+*
+*   http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing,
+* software distributed under the License is distributed on an
+* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+* KIND, either express or implied.  See the License for the
+* specific language governing permissions and limitations
+* under the License.
+*/
+
+import { createChart } from '../../core/utHelper';
+import { EChartsType } from '../../../../src/echarts';
+
+describe('api_getConnectedDataURL', function () {
+
+    let chart: EChartsType;
+    beforeEach(function () {
+        chart = createChart({width: 200, height: 150});
+        chart.setOption({
+            animation: false,
+            xAxis: {type: 'category', data: ['a', 'b']},
+            yAxis: {type: 'value'},
+            series: [{type: 'line', data: [1, 2]}]
+        });
+    });
+    afterEach(function () {
+        chart.dispose();
+    });
+
+    // `opts` is optional — `getDataURL` normalizes it and the reads further down
+    // `getConnectedDataURL` are already written as `opts && opts.xxx`. Only the
+    // very first read was unguarded, so calling the API with no argument threw.
+    it('should accept being called with no argument', function () {
+        expect(function () {
+            chart.getConnectedDataURL();
+        }).not.toThrow();
+    });
+
+    it('should accept being called with an explicit undefined', function () {
+        expect(function () {
+            chart.getConnectedDataURL(undefined);
+        }).not.toThrow();
+    });
+
+    it('should still accept an options object', function () {
+        expect(function () {
+            chart.getConnectedDataURL({type: 'png'});
+        }).not.toThrow();
+    });
+
+});