Alt missing

<a href="https://site.com/pics/picture1.png" target="_blank" rel="..." title="123456"><img src="https://site.com/pics/picture1.png" alt="654321" width="628" height="427" class="aligncenter" /></a>

Result

<a href="https://site.com/pics/picture1.png" target="_blank" rel="..." title="123456"><amp-img src="https://site.com/pics/picture1.png" width="628" height="427" class="aligncenter amp-wp-enforced-sizes" sizes="(min-width: 628px) 628px, 100vw"></amp-img></a>

Alt missing ??