Other Amounts on membership contribution is required

1.7.9379 and also replicated on drupal demo here: https://demo.civicrm.org/drupal/civicrm/contribute/transact?reset=1&action=preview&id=6

The "other amounts" section of the contribution form shows up as being required. I am under the impression that this should be optional as form says "Check this box if you want to give users the option to enter their own contribution amount. Your page will then include a text field labeled Other Amount."