diff --git a/model/DataObject.php b/model/DataObject.php
index baf21d144..3b033b4bc 100644
--- a/model/DataObject.php
+++ b/model/DataObject.php
@@ -1359,7 +1359,7 @@ class DataObject extends ViewableData implements DataObjectInterface, i18nEntity
 			
 		// get filter
 		$combinedFilter = "\"$joinField\" = '$id'";
-		if($filter) $combinedFilter .= " AND {$filter}";
+		if(!empty($filter)) $combinedFilter .= " AND ({$filter})";
 			
 		return singleton($componentClass)->extendedSQL($combinedFilter, $sort, $limit, $join);
 	}