<!DOCTYPE html>
<style>
#transformed {
    overflow: hidden;
    transform: translateZ(0);
    height: 100px;
    width: 100px;
    background-color: salmon;
}
#fixed {
    position: fixed;
    background-color: chartreuse;
    width: 100px;
    height: 100px;
    top: -50px;
}
</style>
<div id="transformed">
  <div id="fixed"></div>
</div>