How to change the license file linked by "View license" button?

When clicking on the “View license” button in my GitHub repository, it takes me to “license.po” file. This file is in my repository root directory and is a Gettext translation file, not a license file. I tried adding a proper LICENSE file to the repository, however this “View license” still links the “license.po”.

How can I change the file the “View license” button links to (i.e. to LICENSE instead of “license.po”) ?