Month/Year format for Custom Field will not accept valid date when used in a profile

Reproduced on demo site.

Create a custom field and use a "month and year" only option on the date format, such as (M yyyy). For example:
http://drupal.demo.civicrm.org/civicrm/admin/custom/group/field/update?action=update&reset=1&gid=1&id=7

Now use this field in a profile. It will not accept any date entered, and rejects as invalid. Example:
http://drupal.demo.civicrm.org/civicrm/profile/create?gid=1&reset=1