Safaricaom Daraja API Android initialization failure (DarajaListener<AccessToken!>! was expected)

This is the way to initialize the Daraja API in Kotlin. Problem is, I get a type mismatch on the forth parameter of Dajara.with(1st, 2nd, 3rd, 4th) function. The error is at the object : DarajaListener parameter.

   daraja = Daraja.with("CONSUME_KEY", "CONSUMER_SECRET_KEY", Env.SANDBOX,
        **object : DarajaListener<AccessToken>**  {
            override fun onResult(result: AccessToken) {
                Toast.makeText(applicationContext, result.access_token, Toast.LENGTH_SHORT).show()
            }

            override fun onError(error: String?) {
                Toast.makeText(applicationContext, error.toString(), Toast.LENGTH_SHORT).show()
            }

        })

The build error is as follows:

Type mismatch: inferred type is but DarajaListener<AccessToken!>! was expected

Hovering the cursor around the error flashes this message:

Type mismatch. Required:DarajaListener<AccessToken!>!Found:

Any help initializing it the right way?