native custom element issue

[GordonSmith]

I am getting the following warning:

[Vue warn]: Failed to resolve component: hpcc-sankey
If this is a native custom element, make sure to exclude it from component resolution via compilerOptions.isCustomElement. 
  at <Sankey> 
  at <VitePressContent class="content" > 
  at <Page key=3 > 
  at <Layout> 
  at <VitePressApp>

Which is supposed to be fixed with: #215

My config file looks like this, I am pretty sure I tried every plausible combination of nesting the relevant options:

module.exports = {
  lang: 'en-US',
  title: '@hpcc-js/web-components',
  description: 'HPCC Systems Custom Web Components',
  base: '/hpcc-js-wc/',

  themeConfig: {
...
  },

  vueOptions: {
    template: {
      compilerOptions: {
        isCustomElement: (tag) => {
          return tag.toLowerCase().indexOf("hpcc-") === 0;
        }
      }
    }
  },

  markdown: {
    config: (md) => {
...
    }
  }
}

[GordonSmith]

FWIW here is the correct setting:

    vue: {
        template: {
            compilerOptions: {
                isCustomElement: (tag) => {
                    return tag.toLowerCase().indexOf("XXX-") === 0;
                }
            }
        }
    },