InSync is the opposite of RequiresRestart...

cmd/syncthing/gui.go

@@ -346,7 +346,7 @@ func restPostConfig(m *model.Model, w http.ResponseWriter, r *http.Request) {
 
 		// Activate and save
 
-		configInSync = config.ChangeRequiresRestart(cfg.Raw(), newCfg)
+		configInSync = !config.ChangeRequiresRestart(cfg.Raw(), newCfg)
 		cfg.Replace(newCfg)
 		cfg.Save()
 	}