diff --git a/op/op.AddDocument.php b/op/op.AddDocument.php
index dd0207439..d30e87e6d 100644
--- a/op/op.AddDocument.php
+++ b/op/op.AddDocument.php
@@ -305,7 +305,7 @@ for ($file_num=0;$file_num<count($_FILES["userfile"]["tmp_name"]);$file_num++){
 			$res = $document->addNotify($user->getID(), true);
 		}
 		/* Check if additional notification shall be added */
-		if($_POST['notification_users']) {
+		if(!empty($_POST['notification_users'])) {
 			foreach($_POST['notification_users'] as $notuserid) {
 				$notuser = $dms->getUser($notuserid);
 				if($notuser) {
@@ -314,7 +314,7 @@ for ($file_num=0;$file_num<count($_FILES["userfile"]["tmp_name"]);$file_num++){
 				}
 			}
 		}
-		if($_POST['notification_groups']) {
+		if(!empty($_POST['notification_groups'])) {
 			foreach($_POST['notification_groups'] as $notgroupid) {
 				$notgroup = $dms->getGroup($notgroupid);
 				if($notgroup) {