setPaymentBlock in MembershipRenewal.tpl gets wrong memType for CC renewals

setPaymentblock() in MembershipRenewal.tpl contains the following line:

var memType = cj('#membership_type_id\\[1
]').val( );

For CC renewals (live mode), memType is always "0" regardless of the true value of the user's renewing membership type. (There is no membership type == 0 in my installation.)

Presumably the selected value of #membership_type_id[1] is set in MembershipRenewal.php but I have been unable to understand why it is failing

setPaymentBlock() then tries to use the value of the undefined expression allMemberships[memType]['total_amount'] to update the displayed membership price, which always fails.

This is causing cividiscount to fail when using a discount code for live CC renewal in my installation.