diff --git a/interface.php b/interface.php
index e9c04da..240d785 100644
--- a/interface.php
+++ b/interface.php
@@ -538,6 +538,7 @@ function create_update_group(ReqHandler &$rh, array $params): string
 {
     global $user;
     global $groupMgr;
+    global $userMgr;
 
     $update = $params[ReqHandler::ACTION_KEY] === "update_group";
     $groupname = trim($params["groupname"]);
@@ -557,7 +558,11 @@ function create_update_group(ReqHandler &$rh, array $params): string
                 $group->disableAutoStoring();
                 $group->setName($groupname);
                 $group->setDescription($description);
-                $group->setOwner($owner);
+
+                // only an existing user might be an owner of a group
+                if ($userMgr->getUser($owner) !== null) {
+                    $group->setOwner($owner);
+                }
 
                 $editors = array_intersect($editors, $group->getMembers()); // a user cannot be an editor if not participant of the group
                 $group->setEditors($editors);
diff --git a/js/groupmgr.js b/js/groupmgr.js
index 172de25..67d8b15 100644
--- a/js/groupmgr.js
+++ b/js/groupmgr.js
@@ -76,6 +76,7 @@ function create_edit_group(group = null) {
             };
             if (update) {
                 req["id"] = group["_id"];
+                req["owner"] = group_ownerF.value
             }
             request(req).then(resp => {
                 list_all_groups();
@@ -163,5 +164,7 @@ function change_group_members() {
     request(req).then(resp => {
         userListTA.value = "";
         hide("member_manager_window");
+        hide("group_editor_window");
+        list_all_groups();
     });
 }
\ No newline at end of file