diff --git a/CHANGELOG.md b/CHANGELOG.md
index de31d85..d18ae1e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 6.5.3
+
+* Fixed default behavior for `notMerge` option (#691).
+
 ## 6.5.2
 
 * Added `dist/csp/*` to support strict CSP with extracted CSS file.
diff --git a/README.md b/README.md
index ab29fda..fc88321 100644
--- a/README.md
+++ b/README.md
@@ -224,13 +224,11 @@ Drop `<script>` inside your HTML file and access the component via `window.VueEC
 <summary>Vue 3 <a href="https://stackblitz.com/edit/vue-echarts-vue-3-global?file=index.html">Demo →</a></summary>
 
 <!-- vue3Scripts:start -->
-
 ```html
 <script src="https://cdn.jsdelivr.net/npm/vue@3.2.45"></script>
 <script src="https://cdn.jsdelivr.net/npm/echarts@5.4.1"></script>
-<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.2"></script>
+<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.3"></script>
 ```
-
 <!-- vue3Scripts:end -->
 
 ```js
@@ -246,13 +244,11 @@ app.component('v-chart', VueECharts)
 <summary>Vue 2 <a href="https://stackblitz.com/edit/vue-echarts-vue-2-global?file=index.html">Demo →</a></summary>
 
 <!-- vue2Scripts:start -->
-
 ```html
 <script src="https://cdn.jsdelivr.net/npm/vue@2.7.14"></script>
 <script src="https://cdn.jsdelivr.net/npm/echarts@5.4.1"></script>
-<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.2"></script>
+<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.3"></script>
 ```
-
 <!-- vue2Scripts:end -->
 
 ```js
diff --git a/README.zh-Hans.md b/README.zh-Hans.md
index 87dcb2e..9a06c3e 100644
--- a/README.zh-Hans.md
+++ b/README.zh-Hans.md
@@ -227,7 +227,7 @@ import "echarts";
 ```html
 <script src="https://cdn.jsdelivr.net/npm/vue@3.2.45"></script>
 <script src="https://cdn.jsdelivr.net/npm/echarts@5.4.1"></script>
-<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.2"></script>
+<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.3"></script>
 ```
 <!-- vue3Scripts:end -->
 
@@ -247,7 +247,7 @@ app.component('v-chart', VueECharts)
 ```html
 <script src="https://cdn.jsdelivr.net/npm/vue@2.7.14"></script>
 <script src="https://cdn.jsdelivr.net/npm/echarts@5.4.1"></script>
-<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.2"></script>
+<script src="https://cdn.jsdelivr.net/npm/vue-echarts@6.5.3"></script>
 ```
 <!-- vue2Scripts:end -->
 
diff --git a/package.json b/package.json
index 2f2b82b..bc843f4 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "vue-echarts",
-  "version": "6.5.2",
+  "version": "6.5.3",
   "description": "Vue.js component for Apache ECharts.",
   "author": "GU Yiling <justice360@gmail.com>",
   "scripts": {
diff --git a/src/ECharts.ts b/src/ECharts.ts
index 1f576f5..c3d9219 100644
--- a/src/ECharts.ts
+++ b/src/ECharts.ts
@@ -232,8 +232,11 @@ export default defineComponent({
               if (!chart.value) {
                 init();
               } else {
+                console.log(`notMerge: ${option !== oldOption}`);
                 chart.value.setOption(option, {
-                  notMerge: option.value !== oldOption?.value,
+                  // mutating `option` will lead to `notMerge: false` and
+                  // replacing it with new reference will lead to `notMerge: true`
+                  notMerge: option !== oldOption,
                   ...realUpdateOptions.value
                 });
               }