diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index daa29cc6..02a690c6 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -1104,7 +1104,7 @@ namespace WebSocketSharp.Net
     protected void AddWithoutValidate (string headerName, string headerValue)
     {
       headerName = checkName (headerName, "headerName");
-      headerValue = checkValue (headerValue);
+      headerValue = checkValue (headerValue, "headerValue");
 
       var headerType = getHeaderType (headerName);