WebSocket gracefull shutdown exception

Hi,
I have regular .net clients and aspNetCore server. When client closes I call webSocket.CloseOutputAsync. This works, I get no exceptions on client or server.

But when trying to do the same on server, it always generate exception, and I tried both webSocket.CloseAsync or webSocket.CloseOutputAsync. With webSocket.CloseOutputAsync I get an exeption on server happens here in WebSocketMessageHandler.cs:

      if (result.MessageType == WebSocketMessageType.Close)
                    {
                        await this.WebSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closed as requested.", CancellationToken.None).ConfigureAwait(false);
                        return null;
                    }

Exception thrown: 'System.Net.WebSockets.WebSocketException' in System.Private.CoreLib.dll
The WebSocket is in an invalid state ('Closed') for this operation. Valid states are: 'Open, CloseReceived, CloseSent'

I changed the code to this and it seems to fix the exception, but not sure if its the correct fix:

if (result.MessageType == WebSocketMessageType.Close)
                    {
                        if (this.WebSocket.State == WebSocketState.CloseReceived)
                            await this.WebSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "Closed as requested.", CancellationToken.None).ConfigureAwait(false);
                        return null;
                    }

Start in WebSocketMessageHandler.cs at the WebSocketMessageType.Close branch and trace the WebSocket state before CloseAsync or CloseOutputAsync is called. Reproduce the server-side close with the described .NET client and verify that graceful shutdown does not attempt an invalid operation or raise WebSocketException.