Though that just kicks the can. We sell support contracts so everyone does a bunch of bug fixing as a matter of course, and that doesn't even get called maintenance internally. "Maintenance" is the refactoring or other tech debt quashing that the devs always want to do but which mostly isn't a priority.
Where I am working bug fixing was always classified as maintenance work. That is even relevant for taxes, as ticket processing is a different category, with different tax rules.
