Not working with extension css

[Yuriy-Svetlov]

Works fine! .scss

gulp.task('callback', function () {
    return watch('src/**/*.scss', function () {
        gulp.src('src/**/*.scss')
            .pipe(gulp.dest('build'))
            .pipe(livereload({ start: true }));
    });
});

Not working .css

gulp.task('callback', function () {
    return watch('src/**/*.css', function () {
        gulp.src('src/**/*.css')
            .pipe(gulp.dest('build'))
            .pipe(livereload({ start: true }));
    });
});

[Yuriy-Svetlov]

I have CSS files in non-web directories. I think this is a problem.