Robo\Collection\CollectionBuilder does not implement CommandInterface

[burzum]

I've checked out the latest version of Robo using ~1 in my composer require. Then I've taken the simple example from the documentation because it is basically already what I want.

class RoboFile extends \Robo\Tasks {

    public function deploy() {
        $gitTask = $this->taskGitStack()
            ->pull();

        $this->taskSshExec('mysite.com')
            ->remoteDir('/var/www/somesite')
            ->exec($gitTask)
            ->run();
    }
}

Then I ran robo deploy and got this:

λ .\bin\robo deploy
in task Robo\Task\Remote\Ssh

Robo\Collection\CollectionBuilder does not implement CommandInterface, so can't be passed into this task