Babel complains about unexpected character '#'?

[melanki]

When importing my custom node package Babel(?) complains about Unexpected character '#' in fetch-blob/index.js which seems to be part of one of my cust package dependencies 'node-fetch'

Module parse failed: Unexpected character '#' (47:2)
File was processed with these loaders:
 * ./node_modules/babel-loader/lib/index.js
You may need an additional loader to handle the result of these loaders.
| const _Blob = class Blob {
|   /** @type {Array.<(Blob|Uint8Array)>} */
>   #parts = [];
|   #type = '';
|   #size = 0;