diff --git a/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php b/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
index 0b6efe328..ae7b927a6 100644
--- a/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
+++ b/src/Bundle/ChillPersonBundle/Entity/AccompanyingPeriod.php
@@ -53,7 +53,7 @@ use Symfony\Component\Validator\GroupSequenceProviderInterface;
 
 use UnexpectedValueException;
 
-use function in_array;
+use function array_key_exists;
 use const SORT_REGULAR;
 
 /**
@@ -644,16 +644,18 @@ class AccompanyingPeriod implements
 
     public function getCenters(): ?iterable
     {
+        $centers = [];
+
         foreach ($this->getPersons() as $person) {
             if (
-                !in_array($person->getCenter(), $centers ?? [], true)
-                && null !== $person->getCenter()
+                null !== $person->getCenter()
+                && !array_key_exists(spl_object_hash($person->getCenter()), $centers)
             ) {
-                $centers[] = $person->getCenter();
+                $centers[spl_object_hash($person->getCenter())] = $person->getCenter();
             }
         }
 
-        return $centers ?? null;
+        return array_values($centers);
     }
 
     /**