diff --git a/VERSIONS_HOTLINE/55376 b/VERSIONS_HOTLINE/55376
new file mode 100644
index 0000000000000000000000000000000000000000..274a083a99f731ed94a7765f6fef3c6411c5e88d
--- /dev/null
+++ b/VERSIONS_HOTLINE/55376
@@ -0,0 +1 @@
+ - ticket #55376 : Administration : optimisation du temps d'affichage des destinataires des newsletters
\ No newline at end of file
diff --git a/library/Class/Migration/NewsletterSubscriptionMigration.php b/library/Class/Migration/NewsletterSubscriptionMigration.php
index b53bcb5ea83c0647b79c215876dd869c64d59212..a507d27d21b3818db880520af234b2a44cd22df3 100644
--- a/library/Class/Migration/NewsletterSubscriptionMigration.php
+++ b/library/Class/Migration/NewsletterSubscriptionMigration.php
@@ -79,7 +79,12 @@ class Class_Migration_NewsletterSubscriptionMigration {
       if ($newsletter->getAutoSubscribe() && $user->isAbonne())
         continue;
 
-      $newsletter->subscribeToDedicatedGroup($user);
+      $group = $newsletter->getDedicatedGroup();
+
+      $attribs = ['user_id' => $user->getId(),
+                  'user_group_id' => $group->getId()];
+      if (!Class_UserGroupMembership::findFirstBy($attribs))
+        Class_UserGroupMembership::newInstance($attribs)->save();
     }
   }
 }
\ No newline at end of file
diff --git a/library/Class/UserGroup.php b/library/Class/UserGroup.php
index e11a0c4349cd5e4e04ec65a24b4f9e53e63b6e46..f0e3a6ce29e3dcaa2522b68977364f591f7f27ea 100644
--- a/library/Class/UserGroup.php
+++ b/library/Class/UserGroup.php
@@ -286,7 +286,7 @@ class Class_UserGroup extends Storm_Model_Abstract {
 
   public function hasUser($user) {
     if ($this->isManual())
-      return in_array($user->getId(), $this->getUsersIds());
+      return in_array($user->getId(), $this->getUsersIdsOptimized());
 
     if ($user->getRoleLevel() != $this->getRoleLevel())
       return false;
diff --git a/library/storm b/library/storm
index 57fb2c7f9ae96f2cb825484e4576619ffa2d91e7..253f43f3a244fcab21498448f93b0bba7aa54ce5 160000
--- a/library/storm
+++ b/library/storm
@@ -1 +1 @@
-Subproject commit 57fb2c7f9ae96f2cb825484e4576619ffa2d91e7
+Subproject commit 253f43f3a244fcab21498448f93b0bba7aa54ce5