I've assigned page for 404 error handling (example.com/404).
I've created Rules condition: Data to compare: [site:current-page:url], Data value: 404.
And I've created some Rules action for this case.
But when I open nonexistent page (example.com/wrong) - there is no corresponding Rules action.
It is because I see 'example.com/wrong' address instead of 'example.com/404'
But how can I create Rules condition for event when 404 error generated?