diff --git a/frontend-js/src/main/js/ServerConnector.js b/frontend-js/src/main/js/ServerConnector.js
index dff12e596fa6ee78124433336faf890e7f987d44..8801a35ab120a35a26c219803fb6108e45debece 100644
--- a/frontend-js/src/main/js/ServerConnector.js
+++ b/frontend-js/src/main/js/ServerConnector.js
@@ -811,7 +811,7 @@ ServerConnector.getProject = function (projectId) {
       return null;
     } else {
       var downloadedProject = new Project(content);
-      if (self._projectsById[projectId] !== undefined) {
+      if (self._projectsById[projectId] instanceof Project) {
         self._projectsById[projectId].update(downloadedProject);
       } else {
         self._projectsById[projectId] = downloadedProject;
@@ -956,7 +956,7 @@ ServerConnector.getProjects = function (reload) {
       self._projects.length = 0;
       for (var i = 0; i < parsedData.length; i++) {
         var project = new Project(JSON.stringify(parsedData[i]));
-        if (self._projectsById[project.getProjectId()] !== undefined) {
+        if (self._projectsById[project.getProjectId()] instanceof Project) {
           self._projectsById[project.getProjectId()].update(project);
         } else {
           self._projectsById[project.getProjectId()] = project;