Safari Technology Preview Build cr… | Apple Developer Forums

Safari Technology Preview Build crashes on creating ShadowRealm object

I have downloaded Safari Technology Preview Build from https://developer.apple.com/safari/download/ (Release 139, posted on January 26, 2022) I am using following command to run Safari:

env JSC_useShadowRealm=1 __XPC_JSC_useShadowRealm=1 /Applications/Safari\ Technology\ Preview.app/Contents/MacOS/Safari\ Technology\ Preview

I created an html file:

<!DOCTYPE html>
<html>
<body>
    <button id="button1">Click Me</button>
</body>
<script type="text/javascript">
    document.getElementById("button1").addEventListener("click", () => {
        var sr = new ShadowRealm();
    });
</script>
</html>

When I click the button the webpage crashes. Please let me know if I am doing anything wrong here. Do I need to use any other environment setting in order to use ShadowRealm?