diff --git a/source/Cosmos.System2_Plugs/System/UInt64Impl.cs b/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
index a8c86b9b8..5bc7cacbe 100644
--- a/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
+++ b/source/Cosmos.System2_Plugs/System/UInt64Impl.cs
@@ -1,5 +1,6 @@
 using System;
 using Cosmos.Common;
+using Cosmos.Common.Extensions;
 using IL2CPU.API;
 using IL2CPU.API.Attribs;