diff --git a/core/attributedef.class.inc.php b/core/attributedef.class.inc.php
index c30a8389be..cfaafad93c 100644
--- a/core/attributedef.class.inc.php
+++ b/core/attributedef.class.inc.php
@@ -8542,7 +8542,7 @@ public function Fingerprint($value)
 		$sFingerprint = '';
 		if ($value instanceOf ormDocument)
 		{
-			$sFingerprint = md5($value->GetData());
+			$sFingerprint = $value->GetSignature();
 		}
 
 		return $sFingerprint;
diff --git a/core/ormdocument.class.inc.php b/core/ormdocument.class.inc.php
index 2ee6dfd33e..4eb53ebde7 100644
--- a/core/ormdocument.class.inc.php
+++ b/core/ormdocument.class.inc.php
@@ -343,6 +343,6 @@ public static function DownloadDocument(WebPage $oPage, $sClass, $id, $sAttCode,
 	 */
 	public function GetSignature(): string
 	{
-		return md5($this->GetData());
+		return md5($this->GetData() ?? '');
 	}
 }