get_ava: illegal value with translucent proxy

Hi, I've setup a translucent proxy. Now, I have tried to do some test searches. For example this works ok: ldapsearch -x -W -D "cn=admin,dc=company,dc=com" -b "OU=Users,OU=Department,DC=company,DC=com" "(givenName=Myname)" Search is proxied through proxy to the actual server, and correct result is returned. However, if I try this: ldapsearch -x -W -D "cn=admin,dc=company,dc=com" -b "OU=Users,OU=Department,DC=company,DC=com" "(objectClass=User)" I get no results. I have monitored the traffic between proxy and backend server, and the query is not even sent there. In OpenLDAP log there is: Jul 27 15:51:00 ldaptr01 slapd[17772]: begin get_filter Jul 27 15:51:00 ldaptr01 slapd[17772]: EQUALITY Jul 27 15:51:00 ldaptr01 slapd[17772]: get_ava: illegal value for attributeType objectClass Jul 27 15:51:00 ldaptr01 slapd[17772]: end get_filter 0 What would be the problem here? Regards, Petteri Heinonen