Universal Olinks in DB5

I was trying to use 
the universal olinking in a DB5 book (the latest DB tools release) and it seems 
to fail.

 

I used the following 
markup:

<firstterm xl:href="#RootResourceClass" xl:role="http://docbook.org/xlink/role/olink">root resource class</firstterm>

 

When building the source I got an error saying invalid olink cannot 
find match for " / ".

When I used a regular olink element everything worked as 
expected.

Is this a known issue or a bug that could be caused by my 
customization layer?