indexterm does not show

[Mansour <mansour77@yahoo.com>]

Hello everyone:
I am having a small problem with my index term. I am trying to produce 
pdf and the indexterm do not show on the page where they are expected. I 
have searched in the fo document and found they commented out.
For example, I have this in my docbook file:

<indexterm><primary>attributes</primary></indexterm>

The resulting fo document has this :

<fo:wrapper id="N20073"><!--attributes--></fo:wrapper>


I am wondering if anyone else is getting this problem. docbook-xsl-1.73.2