diff --git a/README.md b/README.md
index e62dfd1..66c3273 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,12 @@ After installation you need to import and register web component:
 import CodersrankSummary from '@codersrank/summary';
 
 // register web component as <codersrank-summary> element
-window.customElements.define('codersrank-summary', CodersrankSummary);
+function defineCustomElement(name, constructor) {
+  if (!window.customElements.get(name)) {
+    window.customElements.define(name, constructor);
+  }
+}
+defineCustomElement('codersrank-summary', CodersrankSummary.constructor);
 ```
 
 ## Install from CDN