Problem adding TLS to OpenLDAP Ubuntu 16.04

Setting up an OpenLDAP server. I notice the documentation isn't up to date for version 16. For example, the docs refer to the hdb backend instead of the mdb, dc=example,dc=com isn't automatically created, etc...

When I get to the section on adding TLS https://help.ubuntu.com/lts/servergu...l#openldap-tls, all goes well until I try to add the certificate files to LDAP. I create the certinfo.ldif file as described, but when I run it I get this:

root@ldap:~# ldapmodify -Y EXTERNAL -H ldapi:/// -f certinfo.ldif
SASL/EXTERNAL authentication started
SASL useame: gidNumber=0+uidNumber=0,cn=peercred,cn=exteal,cn =auth
SASL SSF: 0
modifying entry "cn=config"
ldap_modify: Other (e.g., implementation specific) error (80)

Here is my certinfo.ldif:

dn: cn=config
add: olcTLSCACertificateFile
olcTLSCACertificateFile: /etc/ssl/certs/cacert.pem
-
add: olcTLSCertificateFile
olcTLSCertificateFile: /etc/ssl/certs/ldap_slapd_cert.pem
-
add: olcTLSCertificateKeyFile
olcTLSCertificateKeyFile: /etc/ssl/private/ldap_slapd_key.pem

I have no clue what's wrong or where to look. Suggestions?