Xinha appends sequence number to internal link when linking to the document multiple times

When adding an internal link to "document x" the first time, the correct anchor is created by Xinha.
<a href="projecten/over-projecten">Projecten</a>

When I add more links to the same internal document, the anchor href is modified by Xinha
<a href="projecten/over-projecten_1">Second link to projecten</a>
<a href="projecten/over-projecten_2">Third link to projecten</a>

Of course I could modify the sitemap so that these links will match, but I think this behavior is not wanted.