diff --git a/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs b/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
index 4c3e4c8cc8..02ed046576 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Http/SocketOutput.cs
@@ -4,6 +4,7 @@
 using Microsoft.AspNet.Server.Kestrel.Networking;
 using System;
 using System.Threading;
+using System.Threading;
 
 namespace Microsoft.AspNet.Server.Kestrel.Http
 {