Grunt watch task is not starting until the first output to console - node.js

Question

My task configuration works fine but I have annoying issue where the watch task does not start to monitor unless I refresh a page or add a line for console output. So normally I am supposed to get:
Running "watch" task
Waiting...
But I don't get it until some output goes to the console.
Is it a bug?
My config is:
module.exports = function(grunt) {
grunt.initConfig({
concat: {
options: {
separator: '\n\n'
},
dev: {
src: ['ng_app/app.js', 'ng_app/**/*.js'],
dest: 'public/js/app.js'
}
},
less: {
dev: {
files: [
{
expand: true,
cwd: 'styles',
src: ['*.less', '!mixins.less', '!var.less'],
dest: 'public/css/',
ext: '.css'
},
{
expand: true,
cwd: 'styles/views',
src: ['*.less'],
dest: 'public/css/views',
ext: '.css'
}
]
}
},
express: {
dev: {
options: {
script: 'bin/www'
}
}
},
watch: {
options: {
livereload: true
},
express: {
files: ['**/*.js'],
tasks: ['express:dev'],
options: {
spawn: false
}
},
less: {
files: ['styles/**/*.less'],
tasks: ['less'],
options: {
livereload: false
}
},
concat: {
files: ['ng_app/**/*.js'],
tasks: ['concat'],
options: {
livereload: false
}
}
}
});
grunt.loadNpmTasks('grunt-contrib-concat');
grunt.loadNpmTasks('grunt-contrib-less');
grunt.loadNpmTasks('grunt-express-server');
grunt.loadNpmTasks('grunt-contrib-watch');
grunt.registerTask('default', ['concat', 'less']);
grunt.registerTask('server', [ 'express:dev', 'watch' ]);
};