Datetime field errors on save

Problem/Motivation

After update to version 8.x-1.0-beta11 I cannot save entities after update when the Datetime fields are present on the form.

Error: Cannot use object of type Drupal\Core\Datetime\DrupalDateTime as array in Drupal\Core\Datetime\Element\Datetime::validateDatetime() (line 355 of /code/core/lib/Drupal/Core/Datetime/Element/Datetime.php).

Proposed resolution

Revert to version 8.x-1.0-beta10 fixed this issue.

Remaining tasks

Any other solutions are welcome.