Contribution reciept email does not respect mobile phone number

If I:

• create a new profile containging 2 phone numners (primary - phone; primary - mobile)
• create a contribution page (enable email reciept)
• make contribution via form - put different numbers for the two phone numbers)

when the reciept comes through it shows the "phone" number for both "phone" fields - the Mobile number is not displayed.

Is this to do with the smarty template?

I've can reproduce this in a vanilla 4.4, but cannot create a profile with more than one (primary) phone number on the 4.5 demo!