diff --git a/modules/erp/lager/service.php b/modules/erp/lager/service.php
index ebbdd36..2c48c98 100644
--- a/modules/erp/lager/service.php
+++ b/modules/erp/lager/service.php
@@ -492,6 +492,15 @@ function is_qualified_open_lot(PDO $pdo, int $lotId): bool
 
 function sync_open_lot_activation_selection(PDO $pdo, int $productId): void
 {
+    $lockStmt = $pdo->prepare(
+        "SELECT id
+         FROM stock_lot
+         WHERE product_id = :product_id
+           AND status = 'open'
+         FOR UPDATE"
+    );
+    $lockStmt->execute([':product_id' => $productId]);
+
     $qualifiedStmt = $pdo->prepare(
         "SELECT sl.id
          FROM stock_lot sl
@@ -505,8 +514,7 @@ function sync_open_lot_activation_selection(PDO $pdo, int $productId): void
            AND sl.expiry_date IS NOT NULL
            AND sl.purchase_date IS NOT NULL
            AND v.qty_net > 0
-         ORDER BY sl.id
-         FOR UPDATE"
+         ORDER BY sl.id"
     );
     $qualifiedStmt->execute([':product_id' => $productId]);
     $qualifiedIds = array_map('intval', $qualifiedStmt->fetchAll(PDO::FETCH_COLUMN));