diff --git a/typo3/sysext/core/Classes/Configuration/FlexForm/FlexFormTools.php b/typo3/sysext/core/Classes/Configuration/FlexForm/FlexFormTools.php
index 88056cf7973a3fe271dde075a74a8322b4ad2fd7..1399622c1455b2a0fe951e4f6243d796c99ec354 100644
--- a/typo3/sysext/core/Classes/Configuration/FlexForm/FlexFormTools.php
+++ b/typo3/sysext/core/Classes/Configuration/FlexForm/FlexFormTools.php
@@ -777,6 +777,10 @@ class FlexFormTools
         if (!is_array($editData)) {
             return 'Parsing error: ' . $editData;
         }
+        // Check if $dataStructureArray['sheets'] is indeed an array before loop or it will crash with runtime error
+        if (!is_array($dataStructureArray['sheets'])) {
+            return 'Data Structure ERROR: sheets is defined but not an array for table ' . $table . (isset($row['uid']) ? ' and uid ' . $row['uid'] : '');
+        }
         // Traverse languages:
         foreach ($dataStructureArray['sheets'] as $sheetKey => $sheetData) {
             // Render sheet: