diff --git a/UIX/Microsoft/Iris/Session/DeferredCall.cs b/UIX/Microsoft/Iris/Session/DeferredCall.cs
index 189df66..d89d074 100644
--- a/UIX/Microsoft/Iris/Session/DeferredCall.cs
+++ b/UIX/Microsoft/Iris/Session/DeferredCall.cs
@@ -92,7 +92,7 @@ namespace Microsoft.Iris.Session
                     eventHandler(_param, _args);
                     break;
 
-                case IDeferredInvokeItem deferredInvokeItem:
+                case null when _param is IDeferredInvokeItem deferredInvokeItem:
                     deferredInvokeItem.Dispatch();
                     break;