Another possible solution that may work is to change the port number (assuming this is a GC server):
If you were using the port 389 change it to 3268
If you were using the port 636 change it to 3269
This may work because (and I quote):
A GC (global catalog) server returns referrals on 389 to refer to the
greater AD “forest”, but acts like a regular LDAP server on 3268 (and
3269 for LDAPS)
It worked for me.
I found this solution in the Shibboleth Users list, answered by Paul Caskey (all the credit to him).
You can check the conversation on this link:
https://lists.internet2.edu/sympa/arc/shibboleth-users/2008-06/msg00039.html