No install link for sub theme of sub theme

Question

In my D8 site I have Magazine Lite, a sub theme of Classy. Magazine Lite is installed.

In web/themes/custom I have a theme installed that in its .info.yml file names Magazine Lite as its base theme.

On the Appearance tab, instead of an install link is the message:

This theme requires the base theme Magazine Lite to operate correctly

In what way does it require the base theme beyond the base theme being present and installed?

Answer 1

Copied the base theme's info file and changed 'name' to 'base theme'. But the base theme entry needs to be the machine name of the theme, whereas the name is a descriptive name.