Boosting field in the mapping file not working with QueryString - symfony

Question

I have an application where the users (clients) can activate different modules.
On the search, the user should be able to search a value in the entire index (for the modules he has activated).
The problem is that I also need to boost some field.
Currently I have this.
mapping.yml
indexes:
traveler:
client: default
finder: ~
types:
Country:
mappings:
name: { boost: 10 }
code:
# additional info (irrelevant)
persistence:
driver: orm
model: CoreBundle\Entity\Country
provider: ~
listener: ~
finder: ~
serializer:
groups: [Default, elastica]
Places:
mappings:
name:
address:
type: "object"
properties:
city: ~
region: ~
country: ~
persistence:
driver: orm
model: CoreBundle\Entity\Places
provider: ~
listener: ~
finder: ~
serializer:
groups: [Default, elastica]
And in my service I have this :
$index = $this->get('fos_elastica.finder.traveler');
$query = new \Elastica\Query\QueryString($search);
# if the client has the module activated
foreach ($this->getClient()->getServices() as $service) {
switch ($service->getService()->getTag()) {
case "countries":
$filters->addShould(
new Type('Country')
);
break;
case "places":
$filters->addShould(
new Type('Places')
);
break;
}
}
$query = new \Elastica\Query\Filtered($query, $filters);
// set result limit
$globalQuery = new Query();
$globalQuery->setQuery($query);
$globalQuery->setSize($limit);
// return result
return $index->find($query);
Now, for example, if I search "Germany", the "Country" result should be first in the result set, because I applied a boost to it in the yml mapping.
Instead, the first 5 or 6 results are for "Places" which have in their country address "Germany".
The boost is not applied (I tried with higher values, removing it ... results are not changed).
I found a way where it works, if I change my service like this, but I would prefer that it use the boost property defined in the mapping.
$query = new QueryString($search);
$query->setFields(array(
'_all',
'Country.name^10'
));
Am I doing something wrong ?
Is there another way to do this ?
Thanks !