Grunt concat generated file has no contents in it

Question

I am using grunt to concat two file. Grunt runs successfully and even create a file but when I open the file, I don't see anything in it. The file is absolutely empty. The contents of my "GruntFile.js" is as under:

grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),

    concat: {
        options: {
            separator: "\n\n"
        },
        dist: {
            src: [
                'overview/js/File1.js',
                'overview/js/File2.js'

            ],
            dest: 'overview/js/build/production.js'
        }
    }
});

// 3. Where we tell Grunt we plan to use this plug-in.
grunt.loadNpmTasks('grunt-contrib-concat');


grunt.registerTask('default', ['concat']);

Any help in this regard would be much appreciated.