Required alternate text not marked with red asterisk

In Drupal 8, an image field can be defined as requiring alternate text. However, if it is so defined, the Alternate Text field on the form is not shown with a red asterisk.

Steps:

As admin:
1. Add an image field to the Basic Page.
2. Check box to allow Alternate text.
3. Check box requiring Alternate text.

As authorized content creator:
4. Click Add content
5. Click Basic page
6. In image field, browse to an image and select it.
7. Click Upload

Actual result: Alternate text field appears. It does not have a red asterisk.
Expected result: Alternate text field appears. It has a red asterisk.