Up: If you do not have this directive in your Vhost, you can also change it more general way instead of doing it for a single site
In case you are on Ubuntu, edit the file /etc/apache2/apache2.conf (here we have an example of /var/www):
<Directory /var/www/>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>
and change it to;
<Directory /var/www/>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>
then,
sudo service apache2 restart