diff --git a/csharp/App/Backend/Controllers/Controller.cs b/csharp/App/Backend/Controllers/Controller.cs
index d9228f964..3cd7cf127 100644
--- a/csharp/App/Backend/Controllers/Controller.cs
+++ b/csharp/App/Backend/Controllers/Controller.cs
@@ -162,14 +162,19 @@ public class Controller : ControllerBase
     
     
     [HttpGet(nameof(GetAllFoldersAndInstallations))]
-    public ActionResult<IEnumerable<TreeNode>> GetAllFoldersAndInstallations(Token authToken)
+    public ActionResult<IEnumerable<Object>> GetAllFoldersAndInstallations(Token authToken)
     {
         var user = Db.GetSession(authToken)?.User;
 
         if (user is null)
             return Unauthorized();
+
+        var foldersAndInstallations = user
+                                     .AccessibleFoldersAndInstallations()
+                                     .OfType<Object>();  // Important! JSON serializer must see Objects otherwise
+                                                         // it will just serialize the members of TreeNode %&@#!!!
         
-        return new (user.AccessibleFoldersAndInstallations());
+        return new (foldersAndInstallations);
     }