diff --git a/websocket-sharp/Net/HttpListener.cs b/websocket-sharp/Net/HttpListener.cs
index 566a463f..a0aa0bdc 100644
--- a/websocket-sharp/Net/HttpListener.cs
+++ b/websocket-sharp/Net/HttpListener.cs
@@ -480,10 +480,8 @@ namespace WebSocketSharp.Net
         EndPointManager.RemoveListener (this);
       }
 
-      lock (_ctxRegistrySync) {
-        if (!force)
-          sendServiceUnavailable ();
-      }
+      lock (_ctxRegistrySync)
+        cleanupContextQueue (!force);
 
       cleanupContextRegistry ();
       cleanupConnections ();