Membership pay later contribution: updating the payment to "complete" extends an annual membership by an additional year

Tested on 4.2.7, 4.2.8 and the current Drupal 7 demo server.

1. Create a membership type of: annual, fixed or rolling
2. Build a contribution page for that membership where payment is "pay later" by default
3. Submit the form to purchase a membership
4. Open the membership record to and edit the contribution, which is currently in "pending" status
5. Edit that record, add the contribution amount, select the payment method and update the status to "Complete"
6. The membership extends itself by an extra year

This also occurs when editing the contribution from the contribution tab, instead of starting from the membership record.

Is there a different way to update the contribution? This felt like the 'intuitive' route