diff --git a/Classes/Utility/UpgradeUtility.php b/Classes/Utility/UpgradeUtility.php
index 1e8c9f0..3174faa 100644
--- a/Classes/Utility/UpgradeUtility.php
+++ b/Classes/Utility/UpgradeUtility.php
@@ -145,7 +145,7 @@ protected function addDataForField(array &$data, array $rawFlexFormData, array $
         }
 
         $dceFieldConfiguration = GeneralUtility::xml2array($dceField['configuration'] ?? '') ?? [];
-        if ($dceFieldConfiguration['type'] === 'group' && ($dceFieldConfiguration['internal_type'] ?? '') === 'file') {
+        if (is_array($dceFieldConfiguration) && $dceFieldConfiguration['type'] === 'group' && ($dceFieldConfiguration['internal_type'] ?? '') === 'file') {
             $filesNames = GeneralUtility::trimExplode(',', $rawFlexFormData[$dceField['variable']] ?? '', true);
 
             $data[$dceField['variable']] = [];
@@ -177,7 +177,7 @@ protected function addDataForField(array &$data, array $rawFlexFormData, array $
                     $this->logger->error($e->getMessage());
                 }
             }
-        } elseif ($dceFieldConfiguration['type'] === 'group' && $dceFieldConfiguration['internal_type'] === 'db' && ($dceFieldConfiguration['appearance']['elementBrowserType'] ?? '') === 'file') {
+        } elseif (is_array($dceFieldConfiguration) && $dceFieldConfiguration['type'] === 'group' && $dceFieldConfiguration['internal_type'] === 'db' && ($dceFieldConfiguration['appearance']['elementBrowserType'] ?? '') === 'file') {
             $fileIds = GeneralUtility::intExplode(',', $rawFlexFormData[$dceField['variable']] ?? '', true);
             $data[$dceField['variable']] = [];
             foreach ($fileIds as $fileId) {
@@ -186,7 +186,7 @@ protected function addDataForField(array &$data, array $rawFlexFormData, array $
 
                 $data[$dceField['variable']][] = $file;
             }
-        } elseif (($dceFieldConfiguration['type'] === 'inline' && ($dceFieldConfiguration['foreign_table'] ?? '') === 'sys_file_reference') || ($dceFieldConfiguration['type'] === 'file')) {
+        } elseif (is_array($dceFieldConfiguration) && (($dceFieldConfiguration['type'] === 'inline' && ($dceFieldConfiguration['foreign_table'] ?? '') === 'sys_file_reference') || ($dceFieldConfiguration['type'] === 'file'))) {
             $data[$dceField['variable']] = [];
 
             /** @var RelationHandler $relationHandler */