How to change this Vue3 ::v-deep SASS syntax to use :deep?

Question

HTML:

<template>
 <form class="bg-white">
  <div class="source-field">
...

Here's the original SASS:

.form::v-deep
  .source-field
    width: 129px
    display: inline-block
    margin: 0px 2px 5px 2px

Changing it to this does not work, none of the styles apply anymore:

:deep(.form)
  .source-field
    width: 129px
    display: inline-block
    margin: 0px 2px 5px 2px