diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index 739817a8..3cc33af4 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -1764,7 +1764,7 @@ namespace WebSocketSharp.Net
       value = checkValue (value);
 
       checkRestricted (name, HttpHeaderType.Request);
-      checkAllowed (false);
+      checkAllowed (HttpHeaderType.Request);
       set (name, value, HttpHeaderType.Request);
     }