"Separate Membership Payment" with Memberships enabled and additional contribution causes incorrect authorize.net transactions

Using the following clean/vanilla setup:
1. WordPress 4.7.2
2. CiviCRM 4.7.16
3. PHP7
4. Authorize.net

If you create contribution page with the following options:
1. Contribution Amounts section enabled
2. Memberships enabled
3. Separate Membership Payment

Authorize.net processes two transactions, but BOTH are for the contribution amount. The membership amount is not processed, and the contribution is set to "Pending (Incomplete Transaction)" in CiviCRM.

I've attached screenshots of one complete transaction and configuration for reference.

Let me know if you need any more info!