Compile Jade with grunt: failed

Question

i'm trying to compile my jade files for an SPA with grunt, and it works ... well, "works..."

my folders:

• app
  • views
    • build
      • any compiled .html
  • any .jade file
• index.jade
• index.html

and my gruntfile.coffee task:

      jade:
        compile:
        options:
          pretty: true
        files:
            [
              extend: true
              flatten: true
              cwd: 'app/views'
              src: '**/*.jade'
              dest: 'app/views/build'
              ext: '.html'
            ]
        compileIndex:
          options:
          pretty: true
          files: 'app/index.html': ['app/index.jade']

Well, i read another questions here like Grunt compiling Jade files but i can get it work fine, when i try to run grunt jade, two things happens; compileIdex works totally fine,but, when compile task run:

Running tasks: jade:compile

Running "jade:compile" (jade) task
Verifying property jade.compile exists in config...OK
Files: prueba.jade -> app/views/build
Options: namespace="JST", separator="\n\n", amd=false, pretty
>> Source file "prueba.jade" not found.
>> Destination not written because compiled files were empty.

So what i'm doing wrong here? I need to keep separate compilations, index and views.