diff --git a/op/op.AddDocument.php b/op/op.AddDocument.php
index 15ab87fef..ef0b66a95 100644
--- a/op/op.AddDocument.php
+++ b/op/op.AddDocument.php
@@ -70,7 +70,7 @@ if($settings->_quota > 0) {
 }
 
 if($user->isAdmin()) {
-	$ownerid = (int) $_POST["ownerid"];
+	$ownerid = !empty($_POST['ownerid']) ? (int) $_POST["ownerid"] : null;
 	if($ownerid) {
 		if(!($owner = $dms->getUser($ownerid))) {
 			UI::exitError(getMLText("folder_title", array("foldername" => $folder->getName())),getMLText("error_occured"));