Using instanceof to detect a pageError

[haveaguess]

I want to detect when a page doesnt exist so Im catching exceptions, and trying to work out if the exception is a pageError.

So Im trying to use :

      if (wikiError instanceof pageError) {

It works if I import the class using :

import { pageError } from "wikipedia/dist/errors";

..but if I use the barrelled main export types from the d.ts like so

import { pageError } from "wikipedia";

It fails with

Right-hand side of 'instanceof' is not an object

Obviously I don't want to rely on digging into the dist folder, any ideas?