is_updated for modifiers

I have scene_update_post handler which checks for updated objects, but it looks like when I change modifier it won’t set is_updated on that object. Is there a way to detect modifier change?

From the wiki, it looks like it should work:

…we can use it to detect if a datablock was updated, requiring e.g. a recalculation of constraints, modifiers, etc.
So I reported a bug: