Using $vm->guestOperationsManager->fileManager fails

[n3r0-ch]

I'm trying to list the files a guest by using the following code:

    public function listFilesInVm(ManagedObject $vm, string $path, $offset = 0, $limit = 50, $pattern = null)
    {
        $this->logger->info('Listing files in '.$path.' of '.$vm->name);

        // Get file manager
        $fileManager = $vm->guestOperationsManager->fileManager;

        // Build args
        $args = [
            'vm' => $vm->getReferenceId(),
            'auth' => $this->getGuestAuthentication(),
            'filePath' => $path,
            'index' => $offset,
            'maxResults' => $limit,
            'matchPattern' => $pattern,
        ];

        $fileManager->ListFilesInGuest($args);
    }

Executing this fails always with the following exception:

  [Vmwarephp\Exception\Soap]
  ServerFaultCode: The request refers to an unexpected or unknown type.. InvalidType: InvalidType Object
  (
      [argument] => Type Mismatch: expected: N3Vim2Vm5Guest11FileManagerE, found: 13FileManagerMo
  )

The same error occurs if I use other methods of the $vm->guestOperationsManager->fileManager. All other request works perfectly

I'm using a vCenter server running 6.5

Any suggestions?