Não atualiza sem F5 Gulp

Está atualizando porém tenho que clicar f5

var gulp = require('gulp'),
    imagemin = require('gulp-imagemin'),
    clean = require('gulp-clean'),
    concat = require('gulp-concat'),
    htmlreplace = require('gulp-html-replace'),
    uglify = require('gulp-uglify')
  ,usemin = require('gulp-usemin')
  ,cssmin = require('gulp-cssmin')
  ,browserSync = require('browser-sync');

gulp.task('default', ['copy'], function() {
    gulp.start('build-img', 'usemin');
});
gulp.task('copy', ['clean'], function() {
    return gulp.src('src/**/*')
        .pipe(gulp.dest('dist'));
});

gulp.task('clean', function() {
    return gulp.src('dist')
        .pipe(clean());
});

gulp.task('build-img', function() {

  gulp.src('dist/img/**/*')
    .pipe(imagemin())
    .pipe(gulp.dest('dist/img'));
});
gulp.task('usemin', function() {
  return gulp.src('dist/**/*.html')
    .pipe(usemin({
      js: [uglify],
      css: [cssmin]
    }))
    .pipe(gulp.dest('dist'));
});
gulp.task('server', function() {
    browserSync.init({
        server: {
            baseDir: 'src'
        }
    });

    gulp.watch('src/**/*').on('change', browserSync.reload);
});

{
  "name": "projeto",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "gulp": "gulp"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "browser-sync": "^2.9.8",
    "gulp": "^3.9.0",
    "gulp-clean": "^0.3.1",
    "gulp-concat": "^2.6.0",
    "gulp-cssmin": "^0.1.7",
    "gulp-html-replace": "^1.5.4",
    "gulp-imagemin": "^2.3.0",
    "gulp-uglify": "^1.4.1",
    "gulp-usemin": "^0.3.14"
  }
}