Installation Wizard is not creating Shared Tables

I am working on a fresh multilingual instalment of Mediawiki. I want to use one database containing 2 languages and some shared tables containing user data. Here is the LocalSettings.php which is used for one of the aforementioned installations: 


## Database settings
$wgDBtype = "mysql";
$wgDBserver = "localhost";
$wgDBname = "wiki_db";
$wgDBuser = "wiki_user";
$wgDBpassword = "_OMITTED_";

# MySQL specific settings
$wgDBprefix = "en_";

# MySQL table options to use during installation or update
$wgDBTableOptions = "ENGINE=InnoDB, DEFAULT CHARSET=binary";

# Shared database table
$wgSharedDB = 'wiki_db';
$wgSharedTables[] = 'actor';
$wgSharedPrefix = 'shared_';


The problem is that no shared table is created. What am I doing wrong?