Judging from the gateway code, it seems to ignore the argspec when the name is prefixed with w_:

```python
        for i, argname in enumerate(code.co_varnames[:code.co_argcount]):
            if argname in self.argspec or argname.startswith("w_"):
                if argname.startswith("w_"):
                    coerce_code = "args_w[{:d}]".format(self.arg_count)
                else:
                    spec = self.argspec[argname]
                    coerce_code = "Coerce.{}(space, args_w[{:d}])".format(spec, self.arg_count)
                lines.append("    if len(args_w) > {}:".format(self.arg_count))
                lines.append("        args += ({},)".format(coerce_code))
                lines.append("    else:")
                if default_start is not None and i >= default_start:
                    lines.append("        args += (defaults[{:d}],)".format(i - default_start))
                else:
                    lines.append("        raise SystemError('bad arg count')")
                self.arg_count += 1
```