```js this.internals.ariaLabelledByElements = [element] // => object is not extensible ``` I guess thats because there is no property `ariaLabelledByElements` and objects are sealed https://github.com/calebdwilliams/element-internals-polyfill/blob/12756b774e683b0cad4b4afbfc4ece6b432ef493/src/element-internals.ts#L101C5-L101C23
I guess thats because there is no property
ariaLabelledByElementsand objects are sealed https://github.com/calebdwilliams/element-internals-polyfill/blob/12756b774e683b0cad4b4afbfc4ece6b432ef493/src/element-internals.ts#L101C5-L101C23