diff --git a/DepotDownloader/DepotDownloaderAuthenticator.cs b/DepotDownloader/DepotDownloaderAuthenticator.cs
index 70184d1a..825ac45b 100644
--- a/DepotDownloader/DepotDownloaderAuthenticator.cs
+++ b/DepotDownloader/DepotDownloaderAuthenticator.cs
@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using System.Threading.Tasks;
 using SteamKit2.Authentication;