Unable to Restrict Page Access when Adaptavist Theme is used

Using a space that has had an Adaptavist Theme applied to it, I've been trying to restrict pages to a user or group without any success.

When entering edit mode for the page, I clicked the EDIT text next to the restriction heading. The dialog appears, I can search groups or type in the name of a person or group that is valid. When I click the "Restrict" button, the field value disappears but no restriction is visible for the page. The auto complete functionality lists me options based on what I type, but the user icon is always grayed out – selection wipes out the value in the field entirely.

The only way I was able to restrict the page was to:

1. Change the theme to a native Confluence theme
2. Navigate back to the page I want to restrict access to
3. The Restriction dialog now displays icons in colour, and clicking the restrict button works
4. Change the theme back to the Adaptavist theme