Error-handling widget

I’m trying to follow the Making an error-handling widget guide. This is my widget code:

    init({ helper }) {
      helper.on('error', () => {
        console.log('Helper Error', arguments);

But the event handler does not get called at all in case of the error (wrong index name, for example). Instead, I see in the console:

events.js:142 Uncaught (in promise) Error: Unhandled error. (undefined)
    at InstantSearch.emit (events.js:142)
    at AlgoliaSearchHelper.<anonymous> (InstantSearch.js:426)
    at AlgoliaSearchHelper.emit (events.js:153)
    at AlgoliaSearchHelper._dispatchAlgoliaError (algoliasearch.helper.js:1331)

Whereas if I add error event listener to the InstantSearch instance, then it gets triggered, and there is no such message in the console log.

What am I doing/understanding wrong?

"algoliasearch": "4.10.3",
"instantsearch.js": "4.25.2-experimental-typescript.0",