cn/approx in openldap 2.0.11

[Allan E Johannesen <aej@WPI.EDU>]

in slapd.conf, the line

index cn approx

causes an error message: "approx index of attribute cn disallowed".  This is a
disappointment, since I used to index it under openldap 1.  Have I done
something wrong?  Can 'cn' (or sn or title) not be indexed this way any more?
Is there some alternative enabling approximate spelling search for names?

I used these schema:

include		/usr/local/etc/openldap/schema/core.schema
include		/usr/local/etc/openldap/schema/cosine.schema
include		/usr/local/etc/openldap/schema/inetorgperson.schema
include		/usr/local/etc/openldap/schema/misc.schema

and some custom schema which, I hope, had no effect.  They didn't redefine
'cn', for example:

include		/usr/local/etc/openldap/schema/eduperson.schema
include		/usr/local/etc/openldap/schema/wpieduperson.schema

Thanks for any guidance anyone can give me...