diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index 3d9aa383..bfbef754 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -1643,7 +1643,7 @@ namespace WebSocketSharp.Net
       var name = getHeaderName (key);
 
       checkRestricted (name, HttpHeaderType.Request);
-      checkAllowed (false);
+      checkAllowed (HttpHeaderType.Request);
       base.Remove (name);
     }