diff --git a/Classes/Utility/ColumnNumberUtility.php b/Classes/Utility/ColumnNumberUtility.php
index f0492e4ad..30b51a61e 100644
--- a/Classes/Utility/ColumnNumberUtility.php
+++ b/Classes/Utility/ColumnNumberUtility.php
@@ -38,7 +38,7 @@ public static function calculateLocalColumnNumber(int $colPos): int
         return (int) $colPos % static::MULTIPLIER;
     }
 
-    public static function calculateParentUid(int $colPos): int
+    public static function calculateParentUid(int|null $colPos): int
     {
         return (int) floor($colPos / static::MULTIPLIER);
     }