diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index 920f0202..3bdfd53e 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -2762,7 +2762,7 @@ namespace WebSocketSharp
 
       byte[] bytes;
       if (!data.TryGetUTF8EncodedBytes (out bytes))
-        throw new ArgumentException ("Could not be UTF8 encoded.", "data");
+        throw new ArgumentException ("It could not be UTF8 encoded.", "data");
 
       send (Opcode.Text, new MemoryStream (bytes));
     }