Centering button with flex box (Safari)

HTML

<div>
  <button>
    <span>Test</span>
    <span>Test</span>
  </button>
  <p>
    <span>Test</span>
    <span>Test</span>
  </p>
</div>

CSS

div{
  display: flex;
  display: -webkit-flex;
  flex-direction: column;
  -webkit-flex-direction: column;
  width: 100%;
}

button, p {
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: row;
  flex-direction: row;
  -webkit-justify-content: center;
  justify-content: center;
}