<!DOCTYPE html>
<html>
  <head>
    <title>Stretchy munderover</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
  </head>
  <body>
    <!-- See bug 687807 -->
    <math>
      <msup>
        <mrow>
          <mrow>
            <munderover>
              <mo stretchy="true">&#x2192;</mo>
              <mtext>AAAAAA</mtext>
              <mtext>BBBBBB</mtext>
            </munderover>
          </mrow>
        </mrow>
        <mtext>CCCCCC</mtext>
      </msup>
    </math>
  </body>
</html>