Google search didn’t get me far, because the only hint I could find was an instruction to SET NAMES ‘UTF8’ in my database connection, but I was already doing that.
Since I used doctrine to save my data, I added the following to my doctrine.global.php:
'params' => array( 'host' => 'localhost', 'port' => '3306', 'dbname' => 'table_name', 'charset' => 'utf8' //<---- here! ...
And suddenly the special chars worked!