Able to delete olcDbIndex config attribute, but not add it.

[Ian Collins]

Hello,

While attempting to add an extra index to an existing config, I was able 
to (accidentally!) delete the attribute, but not add it back:

dn: olcDatabase={1}hdb,cn=config
changetype: modify
delete: olcDbIndex

modifying entry "olcDatabase={1}hdb,cn=config"

dn: olcDatabase={1}hdb,cn=config
changetype: modify
add: olcDbIndex
olcDbIndex: objectClass eq
-

ldapmodify: wrong attributeType at line 8, entry 
"olcDatabase={1}hdb,cn=config"

Is this a bug, or have I done something stupid?

--
Ian.