grunt build fail

[m-misseri]

Hello guys,
i'm trying to build a clean project with maryo and i'm getting:

beax-3411:testprova duco$ grunt build
Running "clean:dist" (clean) task
Cleaning "build/index.html"...OK

Running "useminPrepare:html" (useminPrepare) task
Going through app/index.html to update the config
Looking for build script HTML comment blocks

Configuration is now:

  cssmin:
  { dist: 
   { files: 
      { 'build/styles/main.css': 
         [ '.tmp/styles/{,*/}*.css',
           'app/styles/{,*/}*.css' ] } } }

  concat:
  {}

  uglify:
  {}

  requirejs:
  { dist: 
   { options: 
      { baseUrl: 'app/scripts',
        optimize: 'none',
        preserveLicenseComments: false,
        useStrict: true,
        wrap: true } } }

Running "concurrent:dist" (concurrent) task

    Running "imagemin:dist" (imagemin) task

    Done, without errors.

    Running "htmlmin:dist" (htmlmin) task
    File build/index.html created.

    Done, without errors.

    Running "svgmin:dist" (svgmin) task

    Done, without errors.

Running "requirejs:dist" (requirejs) task
>> Error: Error: Missing either an "out" or "dir" config value. If using "appDir" for a full project optimization, use "dir". If you want to optimize to one file, use "out".
>>     at Function.build.createConfig (/Users/duccio/Sites/testprova/node_modules/grunt-requirejs/node_modules/requirejs/bin/r.js:26817:19)
Warning: Task "requirejs:dist" failed. Use --force to continue.

Aborted due to warnings.

Any hints/ideas?