diff --git a/src/javascript/webgl-rendering-context.js b/src/javascript/webgl-rendering-context.js
index 0319be5e..8e4d8954 100644
--- a/src/javascript/webgl-rendering-context.js
+++ b/src/javascript/webgl-rendering-context.js
@@ -1175,7 +1175,7 @@ class WebGLRenderingContext extends NativeWebGLRenderingContext {
   }
 
   getExtension (name) {
-    const str = name.toLowerCase()
+    const str = name?.toLowerCase()
     if (str in this._extensions) {
       return this._extensions[str]
     }