Link to document within html renders wrong url on site

When I add a link to a document within the html content of a document, it renders the url not in a way I expected. It should render the url with a .html extension similar to the way that is shown when rendering the urls from links in hst:sitemenus.
I tried to find out if the problem was originating from our own content rewriter, but during debugging (and using the SimpleContentRewriter) I found a problem in class org.hippoecm.hst.core.linking.DefaultHstLinkCreator. I used the following setup:
I put a link <a href="testevent"> in document within a document located at /content/documents/NS/test/over-testen/sub2/demo-artikel/demo-artikel.
When I follow the debugger in DefaultHstLinkCreator I get to line 356 where nodePath is set to /content/documents/NS/test/over-testen/sub2/demo-artikel/demo-artikel/nscommon:summary/testevent (where nscommon:summary is the content field). After dereffing the node it is decided on line 365 that this node is not of type NT_DOCUMENT ("hippo:document", I'm guessing that the deref method has returned a hippo:handle instead of the hippo:document?? ) resulting in not setting the representsDocument instance var to true. As a consequence the resolver resolves the link as a link to... I really don't know. Finally the resolver resolves the link to
url /content/documents/NS/test/over-testen/sub1/testevent, which in itself is correct, but it should be /content/documents/NS/test/over-testen/sub1/testevent.html, because the sitemap is configured to use a different template for these specific matchers (* and *.html)
IMHO the link should be dereffed one level deeper to point to the correct node.