diff --git a/databox/api/src/Integration/Phrasea/Expose/ExposeClient.php b/databox/api/src/Integration/Phrasea/Expose/ExposeClient.php
index e5c592aec..5d093d3fd 100644
--- a/databox/api/src/Integration/Phrasea/Expose/ExposeClient.php
+++ b/databox/api/src/Integration/Phrasea/Expose/ExposeClient.php
@@ -255,7 +255,7 @@ public function deleteAsset(IntegrationConfig $config, IntegrationToken $integra
         ;
     }
 
-    private function putPart(string $url, mixed $handleFile, int $partSize, int $retryCount): array
+    private function putPart(string $url, mixed $handleFile, int $partSize, int $retryCount): ?array
     {
         if ($retryCount > 0) {
             $retryCount--;
@@ -267,7 +267,7 @@ private function putPart(string $url, mixed $handleFile, int $partSize, int $ret
                 if ($retryCount == 0) {
                     throw $e;
                 }
-                $this->putPart($url, $handleFile, $partSize, $retryCount);
+                return $this->putPart($url, $handleFile, $partSize, $retryCount);
             }
         }
     }