"gatsby-plugin-sitemap" Cannot read property 'length' of undefined

[xbaha]

Hello,
I copied the exact code here: #22757
but when I tried to add options to sitemap plugin, I got this:

Cannot read property 'length' of undefined

  64 |             }
  65 |
> 66 |             reporter.verbose(_internals.REPORTER_PREFIX + " Filtering " + allPages.length + " pages     based on " + excludes.length + " excludes");

not sure where can I start, I have no clue what the error means.

regards

[mwskwong]

That's a one-year-old code and there has been a major version update with breaking changes since then. You should follow the official documentations first.