enough-namestring doesn't work?

I tried the followin: |(enough-namestring #P"/a/b/c/d.txt" #P"/a/b/")|. 
I was expecting |"c/d.txt"|. But gcl 2.6.13 release returns 
“/a/b/c/d.txt”. I actually can’t find any example where 
|enough-namestring| produces anything other than the namestring for the 
first arg.

How do I invoke |enough-namestring| to produce what I want, like other 
lisps do?

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