RequestSocket crash

[cduret]

Environment

NetMQ Version:    4.0.1.13
Operating System:  WSL2 / Linux Debian
.NET Version:     dotnet sdk 8

I have a crash when using RequestSocket with a pyzmq Response server

server.py (pyzmq version 4.3.5)

import zmq

ctx = zmq.Context()
sock = ctx.socket(zmq.REP)
sock.bind('tcp://localhost:5554')
while True:
  message = sock.recv().decode()
  sock.send('hello {0} !'.format().encode())

client.cs

using System;
using NetMQ;
using NetMQ.Sockets;

namespace Test {
  class Program {
    private static void Main(string[] args) {
      using (var socket = new RequestSocket()) {
        socket.Connect("tcp://localhost:5554");
        socket.SendFrame("world");
        string res = socket.ReceiveFrameString();
        Console.WriteLine(res);
      }
    }
  }
}

Expected behaviour

Expect to have a response: "hello world !"

Actual behaviour

$ ./bin/Debug/net8.0/test 
Process terminated. Assertion failed.
Unexpected null of type Byte[]
   at NetMQ.Assumes.NotNull[T](T o) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Utils/Assumes.cs:line 12
   at NetMQ.Core.Transports.V2Encoder.SizeReady() in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/V2Encoder.cs:line 36
   at NetMQ.Core.Transports.V2Encoder.Next() in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/V2Encoder.cs:line 25
   at NetMQ.Core.Transports.EncoderBase.Encode(ByteArraySegment& data, Int32 size) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/EncoderBase.cs:line 103
   at NetMQ.Core.Transports.StreamEngine.BeginSending() in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 451
   at NetMQ.Core.Transports.StreamEngine.ProcessHandshakeCommand(Msg& msg) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 1186
   at NetMQ.Core.Transports.V2Decoder.PushMsg(ProcessMsgDelegate sink) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/V2Decoder.cs:line 133
   at NetMQ.Core.Transports.StreamEngine.ProcessInput() in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 982
   at NetMQ.Core.Transports.StreamEngine.Handle(Action action, SocketError socketError, Int32 bytesTransferred) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 385
   at NetMQ.Core.Transports.StreamEngine.FeedAction(Action action, SocketError socketError, Int32 bytesTransferred) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 333
   at NetMQ.Core.Transports.StreamEngine.InCompleted(SocketError socketError, Int32 bytesTransferred) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Transports/StreamEngine.cs:line 1008
   at NetMQ.Core.IOObject.InCompleted(SocketError socketError, Int32 bytesTransferred) in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/IOObject.cs:line 108
   at NetMQ.Core.Utils.Proactor.Loop() in /home/cydu/DEV/zmq/netmq-4.0.1.13/src/NetMQ/Core/Utils/Proactor.cs:line 123
Aborted (core dumped)