Dialling a SIP number

So I have a very, very shiny new Nexus 4. This supports SIP, and I have added a SIP account to the telephony accounts settings page. Unfortunately I cannot figure out how to actually *dial* a SIP number. How do I do this? The telephone dialer has number buttons only, and tapping the number entry field doesn't pop up a keyboard. Rumour has it that previous versions of Android had a 'text' button somewhere on the dialer page, but that's not present in JB. There must be some way to do it... (Note: I'm not asking how to add a SIP number to a contact. I know how to do that. I want to dial numbers that aren't on my contacts list.) Update: after some experimenting, I have found that: - pressing the DIAL button with the field empty reloads the text field with the last number dialed, which can be a SIP number of the form sip:music@iptel.org. So I know the text field is *capable* of handling text. - trying to paste text into the field produces gibberish. For the above number, I get 7476874247835.674! (Which is what the letters on the dial pad map to. Except for : and @, which are emitted.) Dialing this number does nothing --- obviously.