diff --git a/modules/erp/lager/service.php b/modules/erp/lager/service.php
index a505d86..ce1af83 100644
--- a/modules/erp/lager/service.php
+++ b/modules/erp/lager/service.php
@@ -365,9 +365,10 @@ function update_stock_lot_traceability(
             throw new InvalidArgumentException('Korrekturen und Abgaenge koennen nur auf der aktiven Charge gebucht werden');
         }
 
+        $lotNumberAssignment = $clearLotNumber ? 'NULL' : 'COALESCE(:lot_number, lot_number)';
         $updateStmt = $pdo->prepare(
             "UPDATE stock_lot
-             SET lot_number = CASE WHEN :clear_lot_number THEN NULL ELSE COALESCE(:lot_number, lot_number) END,
+             SET lot_number = {$lotNumberAssignment},
                  manufacturer_party_id = :manufacturer_party_id,
                  manufacturer_lot_number = :manufacturer_lot_number,
                  mfg_date = :mfg_date,
@@ -376,16 +377,18 @@ function update_stock_lot_traceability(
                  updated_at = NOW()
              WHERE id = :id"
         );
-        $updateStmt->execute([
-            ':lot_number' => $lotNumber,
-            ':clear_lot_number' => $clearLotNumber,
+        $updateParams = [
             ':manufacturer_party_id' => $manufacturerPartyId,
             ':manufacturer_lot_number' => $manufacturerLotNumber,
             ':mfg_date' => $dates['mfg_date'],
             ':expiry_date' => $dates['expiry_date'],
             ':purchase_date' => $dates['purchase_date'],
             ':id' => $lotId,
-        ]);
+        ];
+        if (!$clearLotNumber) {
+            $updateParams[':lot_number'] = $lotNumber;
+        }
+        $updateStmt->execute($updateParams);
 
         $after = $before;
         if ($clearLotNumber) {