选择具有子项的第一个子项列表项

I have the following unordered list item with nested ul. How do I select the first li aka the text "List A" ?

I tried ul > li:first-child but this selects the first list item's child as well.

<ul>
        <li>
          List A
          <ul>
            <li>List A sub</li>
            <li>List A sub</li>
            <li>List A sub</li>
            <li>List A sub</li>
          </ul>
        </li>
        <li>
          List B
          <ul>
            <li>List B sub</li>
            <li>List B sub</li>
            <li>List B sub</li>
            <li>List B sub</li>
          </ul>
        </li>
      </ul>