diff --git a/examples/jsm/webxr/VRButton.js b/examples/jsm/webxr/VRButton.js
index 6856a21b17aa45..81a67f06d172ed 100644
--- a/examples/jsm/webxr/VRButton.js
+++ b/examples/jsm/webxr/VRButton.js
@@ -176,7 +176,7 @@ class VRButton {
 
 	static registerSessionGrantedListener() {
 
-		if ( 'xr' in navigator ) {
+		if ( typeof navigator !== 'undefined' && 'xr' in navigator ) {
 
 			// WebXRViewer (based on Firefox) has a bug where addEventListener
 			// throws a silent exception and aborts execution entirely.