Prevent command shortcuts that are defined in add-on manifest from being executed

My add-on has defined a keyboard shortcut for executing a command via the commands manifest key in manifest.json. However, I don’t want it to be executed in an extension page which is opened in a popup window. Is there a way to suppress keyboard shortcuts defined in add-on manifests?

I tried catching key events (i.e., the “keydown” event) in the extension page and then calling event.preventDefault(), but that didn’t work.