# 13802: Dial: No referUrl attribute specified

Log Type: APPLICATION

Log Level: ERROR

## Description

In order to send a SIP REFER message to an established `<Dial>` call, the `referUrl` attribute must be specified in the TwiML. In this case, a REFER was received on a `<Dial>` call without a `referUrl` attribute present.

### Possible causes

* Your `<Dial>` verb did not include a `referUrl` attribute or the attribute was misspelled

### Possible solutions

* Add a valid `referUrl` attribute to your `<Dial>` verb
* For more information on sending REFER to Twilio, see [Refer to Twilio](/docs/voice/api/refer-to-twilio)