W3 Total Cache not detecting memcached

I would like to use memcached for the database and object cache.
However, I’m not able to select that option. The only option I’m able to select is “Disk”.

Maybe I’m missing something.

Memcached is installed and listening to port 11211 on 127.0.0.1.
Memcached PHP Extension is installed.

It seems like PHP is using memcached:

$ php -r ‘phpinfo();’ | grep ‘memcache’
/etc/php.d/memcached.ini,
memcached
memcached support => enabled
libmemcached version => 1.0.8
memcached.compression_factor => 1.3 => 1.3
memcached.compression_threshold => 2000 => 2000
memcached.compression_type => fastlz => fastlz
memcached.serializer => php => php
memcached.sess_binary => 0 => 0
memcached.sess_connect_timeout => 1000 => 1000
memcached.sess_consistent_hash => 0 => 0
memcached.sess_lock_expire => 0 => 0
memcached.sess_lock_max_wait => 0 => 0
memcached.sess_lock_wait => 150000 => 150000
memcached.sess_locking => 1 => 1
memcached.sess_number_of_replicas => 0 => 0
memcached.sess_prefix => memc.sess.key. => memc.sess.key.
memcached.sess_randomize_replica_read => 0 => 0
memcached.sess_remove_failed => 0 => 0
memcached.sess_sasl_password => no value => no value
memcached.sess_sasl_username => no value => no value
memcached.store_retry_count => 2 => 2
memcached.use_sasl => 0 => 0
Registered save handlers => files user memcached
session.save_handler => memcached => memcached

What am I missing?