diff --git a/src/Service/SyncXxllncCasesService.php b/src/Service/SyncXxllncCasesService.php
index f3a77b1..93cde8d 100644
--- a/src/Service/SyncXxllncCasesService.php
+++ b/src/Service/SyncXxllncCasesService.php
@@ -25,8 +25,8 @@
 /**
  * Service responsible for synchronizing xxllnc cases to woo objects.
  *
- * @author  Conduction BV <info@conduction.nl>, Barry Brands <barry@conduction.nl>, Wilco Louwerse <wilco@conduction.nl>.
- * @license EUPL <https://github.com/ConductionNL/contactcatalogus/blob/master/LICENSE.md>
+ * @author
+ * @license
  *
  * @package  CommonGateway\WOOBundle
  * @category Service
@@ -236,8 +236,8 @@ private function getBijlagen(array $result, array $config, array &$fileURLS): ar
                 $documentMeta     = $result['values']["attribute.woo_$field"][0];
                 $fileURLS[$field] = $this->retrieveFile($result, $documentMeta, $config);
                 $fileNames[]      = $result['values']["attribute.woo_$field"][0]['filename'];
-            }//end if
-        }//end foreach
+            }
+        }
 
         $bijlagen = [];
         if (isset($result['values']["attribute.woo_publicatie"]) === true) {
@@ -246,8 +246,8 @@ private function getBijlagen(array $result, array $config, array &$fileURLS): ar
                     $bijlagen[]  = $this->retrieveFile($result, $documentMeta, $config);
                     $fileNames[] = $documentMeta['filename'];
                 }
-            }//end foreach
-        }//end if
+            }
+        }
 
         return $bijlagen;
 
@@ -313,6 +313,32 @@ private function fetchObjects(Source $source, ?int $page=1, array $results=[]):
     }//end fetchObjects()
 
 
+    /**
+     * Valideert de OIN-waarde om ervoor te zorgen dat deze alleen cijfers bevat.
+     *
+     * @param mixed $oin De OIN-waarde uit de configuratie.
+     *
+     * @return string De gevalideerde OIN-waarde.
+     *
+     * @throws \InvalidArgumentException als de OIN ongeldig is.
+     */
+    private function validateOin($oin): string
+    {
+        // Controleer of de OIN is ingesteld en een niet-lege string is
+        if (!isset($oin) || !is_string($oin) || trim($oin) === '') {
+            throw new \InvalidArgumentException('OIN-waarde ontbreekt of is ongeldig.');
+        }
+
+        // Controleer of de OIN alleen uit cijfers bestaat (voorloopnullen toegestaan)
+        if (!preg_match('/^\d+$/', $oin)) {
+            throw new \InvalidArgumentException('OIN-waarde moet alleen uit cijfers bestaan.');
+        }
+
+        return $oin;
+
+    }//end validateOin()
+
+
     /**
      * Handles the synchronization of xxllnc cases.
      *
@@ -355,7 +381,7 @@ public function syncXxllncCasesHandler(array $data, array $configuration): array
             isset($this->style) === true && $this->style->error("{$this->configuration['source']}, {$this->configuration['schema']} or {$this->configuration['mapping']} not found, ending syncXxllncCasesHandler");
 
             return [];
-        }//end if
+        }
 
         isset($this->style) === true && $this->style->info("Fetching cases from {$source->getLocation()}");
         $this->logger->info("Fetching cases from {$source->getLocation()}", ['plugin' => 'common-gateway/woo-bundle']);
@@ -363,6 +389,15 @@ public function syncXxllncCasesHandler(array $data, array $configuration): array
         $results = $this->fetchObjects($source);
         $this->entityManager->flush();
 
+        // Valideer de OIN-waarde
+        try {
+            $oin = $this->validateOin($this->configuration['oin']);
+        } catch (\InvalidArgumentException $e) {
+            $this->logger->error('Validatie van OIN mislukt: '.$e->getMessage(), ['plugin' => 'common-gateway/woo-bundle']);
+            isset($this->style) === true && $this->style->error('Validatie van OIN mislukt: '.$e->getMessage());
+            return [];
+        }
+
         $idsSynced        = [];
         $responseItems    = [];
         $hydrationService = new HydrationService($this->syncService, $this->entityManager);
@@ -377,7 +412,7 @@ public function syncXxllncCasesHandler(array $data, array $configuration): array
                         'settings'    => ['allowPDFOnly' => $configuration['allowPDFOnly']],
                         'autoPublish' => $this->configuration['autoPublish'] ?? true,
                         'organisatie' => [
-                            'oin'  => $this->configuration['oin'],
+                            'oin'  => $oin,
                             'naam' => $this->configuration['organisatie'],
                         ],
                     ]