Node.js: How to stop a pipe from streaming data

I'm creating a request using the request npm module. However in case the content type is not json, i want the stream to stop. At the moment, it does not stop and and error is generated because unzip reads an invalid header.. How can we stop a stream?

    var req = request(options)
    req
    .on('error', function (err) { console.log("err"); reject(err) })
    .on('response', function(response) { 
        if(response.headers['content-type'] != 'application/json')
        {
            console.log(response.headers['content-type'])
            req.destroy() // doesn't work
            this.destroy() // doesn't work
        }
    })
    .on('end', function () { resolve() })
    .pipe(gunzip)  // ERROR!