How to fix unexpected token "indent" when using pug in vue?

Question

Pug

Hello.
I am using pug(vue-cli-plugin-vue) in a vue3 project.
When I do this

<template lang="pug">
  .app-container
    preloader(v-if="loading" type="preloader")
    router-view
</template>

An error is thrown `unexpected token "indent"`
The problem is that there is a tab on the root DOM element of the vue template

. If you remove the tab, everything works

<template lang="pug">
.app-container
  preloader(v-if="loading" type="preloader")
  router-view
</template>

How can I fix it, google found nothing, saw issues on github nothing sensible