olcDbCacheSize: no equality matching rule

Dear listmembers,

After upgrading from openldap 2.4.21 to 2.4.25 my olcDbCacheSize entry seems to have gone awoll. I tried to fix that with the following ldif file:

dn: olcDatabase={1}hdb,cn=config changetype:modify add: olcDbCachesize olcDbCachesize: 10000

but I got this errormessage:

modifying entry "olcDatabase={1}hdb,cn=config" ldap_modify: Inappropriate matching (18) additional info: modify/add: olcDbCacheSize: no equality matching rule

Does anybody have any idea what is wrong? Many thanks in advance,

Gerard Ranke