I compiled a new instance of OpenLDAP from the git Master and the bug seems to be fixed.

After parsing the git commits, I found a link back to a bug report : http://www.openldap.org/its/index.cgi/Software%20Bugs?id=7975;selectid=7975

It's similar to mine (but didn't come up in my searches, sorry) so my bug report can be closed.

Frederic Jacquot INSA Lyon