Tasks not available?

I must be doing something wrong at the very basic level.

Gem is installed:
```
% bundle list | grep capis
* capistrano (3.16.0)
* capistrano-bundler (2.0.1)
* capistrano-maintenance (1.2.1)
* capistrano-passenger (0.2.1)
* capistrano-rails (1.6.1)
* capistrano-rbenv (2.2.0)
```

But I get:

```
% bundle exec cap staging maintenance:disable
(Backtrace restricted to imported tasks)
cap aborted!
Don't know how to build task 'maintenance:disable' (See the list of available tasks with `cap --tasks`)

(See full trace by running task with --trace)
```

And this is strange:
```
% cap production doctor:gems

Gems

capistrano 3.16.0
airbrussh 1.4.0
rake 13.0.3
sshkit 1.21.2
net-ssh 6.1.0
capistrano-bundler 2.0.1
capistrano-passenger 0.2.1
capistrano-rails 1.6.1
capistrano-rbenv 2.2.0
```

Am I missing a step somewhere?