grunt, grunt-shell and command argument

I would like to pass an argument to grunt-shell like it is defined in the documentation:

module.exports = function(grunt) {

// Configure Grunt
grunt.initConfig({
    shell: {           
        hello: {
            command: function (greeting) {
                return 'echo ' + greeting;
            },
            options: {
                stdout: true
            }
        }

    }
});

grunt.loadNpmTasks('grunt-shell');
grunt.registerTask('d', 'shell:hello');

When I execute it without argument it's working but when I try to put an argument I got an error:

Julio:Server julio$ grunt d
Running "shell:hello" (shell) task
undefined

Done, without errors.
Julio:Server julio$ grunt d:me
Warning: Task "me" not found. Use --force to continue.

Aborted due to warnings.

Where is my misunderstanding?

Thank you