Text input's cursor doesn't move while scrolling the page on iOS

HTML

<div id="container">
  <input type="text" />
  <div class="filling"></div>
</div>

CSS

#container {
  position: absolute;
  top: 20px;
  bottom: 20px;
  width: 50%;
  overflow-y: auto;
  border: 1px solid black;
}

input {
  margin-top: 60vh;
}

.filling {
  height: 200vh;
}