Cannot read property 'files'

[xavierartot]

Hi, I was running: grunt -v I have these error

Running "newer:jade:dev" (newer) task
Options: cache="/Applications/MAMP/htdocs/freecodecamp-lab/workflow/node_modules/grunt-newer/.cache", override=undefined, tolerance=0
Warning: Cannot read property 'files' of undefined Use --force to continue.

Aborted due to warnings.

in my Gruntfile those two files exists: index.html and index.jade

    jade: {
      debug: {
        options: {
          data: {
            debug: true,
            timestamp: "<%= new Date().getTime() %>"
          }
        },
        files: {
          "index.html": "index.jade"
        }
      }
    },

package.json

{
  "name": "freecodeCamp",
  "version": "0.0.1",
  "devDependencies": {
    "load-grunt-tasks": "~1.0.0",
    "time-grunt": "~1.0.0",
    "grunt": "^0.4.5",
    "grunt-contrib-jshint": "~0.10.0",
    "grunt-autoprefixer": "^2.2.0",
    "grunt-concat-sourcemap": "^0.4.3",
    "grunt-contrib-sass": "^0.9.2",
    "grunt-contrib-jade": "^1.0.0",
    "grunt-contrib-uglify": "~0.6.0",
    "grunt-contrib-watch": "~0.6.1",
    "grunt-contrib-concat": "~0.5.0",
    "grunt-newer": "^1.1.1"
  }
}

Thanks