diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index 031a35f7..a60d874f 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -999,7 +999,7 @@ namespace WebSocketSharp.Net
     {
       value = checkValue (value);
 
-      if (IsMultiValue (name, response)) {
+      if (isMultiValue (name, response)) {
         base.Add (name, value);
 
         return;