[LdapAuthenticatorBundle] Error while setting options array in config.yml

[Plopix]

Bundle(s) affected: LdapAuthenticatorBundle

Description
Setting up the options array in config file will resut in a 500 error after login to backend, e.g.

nova_ez_ldap:
connections:
default:
ldap:
adapter:
host: localhost
port: 389
version: 3
encryption: none # One of "none"; "ssl"; "tls"
options:
referrals: false
# or self signed ssl cert from ldap server
#LDAP_OPT_X_TLS_CACERTFILE: '/usr/share/ca-certificates/ldapserver.crt'

After login you will get a 500 error: The option "options" with value array is invalid. [in vendor/symfony/symfony/src/Symfony/Component/OptionsResolver/OptionsResolver.php:797

We tried some differnd config options, but nothhing worked fine.

Originally reported by @bjko Novactive/NovaeZLdapAuthenticatorBundle#2