diff --git a/Classes/BackendLayout/BackendLayoutConfiguration.php b/Classes/BackendLayout/BackendLayoutConfiguration.php
index cd1121d..34f47ec 100644
--- a/Classes/BackendLayout/BackendLayoutConfiguration.php
+++ b/Classes/BackendLayout/BackendLayoutConfiguration.php
@@ -62,7 +62,7 @@ public static function createFromPageId($pageId)
      */
     public function getConfigurationByColPos($colPos, $recordUid = null)
     {
-        $configurationIdentifier = md5($this->backendLayout['config']);
+        $configurationIdentifier = md5((string)$this->backendLayout['config']);
         if (isset(self::$columnConfiguration[$configurationIdentifier][$colPos])) {
             return self::$columnConfiguration[$configurationIdentifier][$colPos];
         }