setsockopt fails when using ZMQ_SWAP

[jonathanstone]

Using version 2.15.3

If I attempt to use ZMQ_SWAP with the setsockopt method as follows:

    this.subSocket = zmq.socket("sub");
    this.subSocket.setsockopt(zmq.ZMQ_SWAP, 10000);

I get an exception as follows:

Error: Invalid argument
at Error (native)

What am I doing wrong?

Thanks for your help.