UPnP specific method (NOTIFY) considered invalid

[sawcce]

Hi there! I'm trying to implement a simple http server to handle gena callbacks in a flutter app that communicates with UPnP devices, as far as I'm aware the NOTIFY and SUBSCRIBE methods aren't part of the HTTP standard (I could be wrong though) which means that I get this error:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument (verb): expected a valid HTTP method: "NOTIFY" at router.dart:131

I don't know if there is a way to override this "checking" behavior which makes it impossible for me to do things as simple as:

    genaRouter.add("NOTIFY", "/callback", (Request request) {
      print(inspect(request));
      return Response.ok("OK!");
    });

A request example I kindly took from a wireshark capture of my local network:
.

If I missed anything that would make it possible to fix this I apologize :)