<!DOCTYPE html>
<html>
  <head>
    <title>Test mpadded</title>
  </head>
  <body>
    <math>
      <mpadded mathbackground="red" width="100width">
        <mphantom>
          <mtext style="font-family: monospace">X</mtext>
        </mphantom>
      </mpadded>
    </math>
    <br>
    <math>
      <mpadded mathbackground="red" width="100width">
        <mphantom>
          <mtext mathvariant="monospace">X</mtext>
        </mphantom>
      </mpadded>
    </math>
  </body>
</html>