can't delete ppolicy overlay from cn=config

[Scott Classen <SClassen@lbl.gov>]

hello,

this is my ldif file:

dn: olcOverlay={1}ppolicy,olcDatabase={1}bdb,cn=config
changetype: delete

command to remove entry:
%ldapmodify -x -D "uid=ldapadmin,ou=peps,dc=example,dc=com" -W -f ppolicy-del.ldif

deleting entry "olcOverlay={1}ppolicy,olcDatabase={1}bdb,cn=config"
ldap_delete: Server is unwilling to perform (53)

I'm performing this operation as rootdn why can I not delete the entry?