visibility:hidden + z-index makes button invisible in Firefox

Question

Check this code

.parent {
  visibility: hidden;
  position: relative;
  z-index: 1;
}

.child {
  visibility: visible;
}

<button class="parent">
      <span class="child">content</span>
 </button>

In Firefox on Mac .child remains invisible.
In chrome and safari .child is visible.

Any ideas how to fix that?

Answer 1

Firefox devs fixed it, bugzilla.mozilla.org/show_bug.cgi?id=1732921