xref to indexterm

I get this:

Don't know what gentext to create for xref to: "indexterm", ("format-dot")

for <xref linkend="format-dot"/>
 <firstterm>~.<indexterm id="format-dot" significance="preferred">
   <primary>&format;</primary>
   <secondary id="format-dot-i">~.</secondary></indexterm></firstterm>
I don't see why the "bottom-most" (in this case, secondary) text cannot
be used as "gentext" for xref to format-dot.

-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
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