[docbook] can an anchor be a target for an olink?

[natk]

I am generating an olink db from a docbook file which contains anchors.

e.g.

<section id="id1">
  <title>Title</title>
  <table border="1">
...
    <tbody>
    <tr>
       <td><anchor id="id2"/>Text</td>
....

The olinkdb file getting generated from this does not produce a title:

<obj element="anchor"
     href="File.html#id2"
     number="" targetptr="id2">
     <ttl>???TITLE???</ttl>
     <xreftext>Section 1.1.3, “Section Title”</xreftext>
</obj>

Are anchors allowed as targets for olinks? If so, what do I need to change?

I am using the maven-docbkx-plugin with version 1.76.1 of the stylesheets.

Nat