diff --git a/server/src/Hubs/DigitalTubesHub.cs b/server/src/Hubs/DigitalTubesHub.cs
index 999d9b7..4eb879f 100644
--- a/server/src/Hubs/DigitalTubesHub.cs
+++ b/server/src/Hubs/DigitalTubesHub.cs
@@ -70,7 +70,7 @@ public class DigitalTubesHub : Hub<IDigitalTubesReceiver>, IDigitalTubesHub
     private readonly IHubContext<DigitalTubesHub, IDigitalTubesReceiver> _hubContext;
     private readonly Database.UserManager _userManager = new();
 
-    private ConcurrentDictionary<string, DigitalTubesScanTaskInfo> _scanTasks = new();
+    private static ConcurrentDictionary<string, DigitalTubesScanTaskInfo> _scanTasks = new();
 
     public DigitalTubesHub(IHubContext<DigitalTubesHub, IDigitalTubesReceiver> hubContext)
     {
diff --git a/server/src/Hubs/OscilloscopeHub.cs b/server/src/Hubs/OscilloscopeHub.cs
index fffd71e..ecf908f 100644
--- a/server/src/Hubs/OscilloscopeHub.cs
+++ b/server/src/Hubs/OscilloscopeHub.cs
@@ -86,7 +86,7 @@ public class OscilloscopeHub : Hub<IOscilloscopeReceiver>, IOscilloscopeHub
     private readonly IHubContext<OscilloscopeHub, IOscilloscopeReceiver> _hubContext;
     private readonly Database.UserManager _userManager = new();
 
-    private ConcurrentDictionary<string, OscilloscopeScanTaskInfo> _scanTasks = new();
+    private static ConcurrentDictionary<string, OscilloscopeScanTaskInfo> _scanTasks = new();
 
     public OscilloscopeHub(IHubContext<OscilloscopeHub, IOscilloscopeReceiver> hubContext)
     {
@@ -192,9 +192,7 @@ public class OscilloscopeHub : Hub<IOscilloscopeReceiver>, IOscilloscopeHub
             var scanTaskInfo = new OscilloscopeScanTaskInfo(client);
             scanTaskInfo.ScanTask = ScanTask(scanTaskInfo, Context.ConnectionId);
 
-            _scanTasks[key] = scanTaskInfo;
-
-            return result.Value;
+            return _scanTasks.TryAdd(key, scanTaskInfo);
         }
         catch (Exception ex)
         {