jekyll: Auto-regeneration not working, even when forced

What version of Jekyll are you using (jekyll -v)?

jekyll 3.0.4

What operating system are you using?

OS X 10.11.4

What did you do?

1. Setup Jekyll GitHub Pages
2. Ran bundle exec jekyll serve as in the guide

What did you expect to see?

Auto-regeneration to be enabled like here.

What did you see instead?

Auto-regeneration disabled with following output (note the deprecation notes):

Configuration file: /Users/glennreyes/p/my-jekyll-site-project-name/_config.yml
       Deprecation: Auto-regeneration can no longer be set from your configuration file(s). Use the --[no-]watch/-w command-line option instead.
            Source: /Users/glennreyes/p/my-jekyll-site-project-name
       Destination: /Users/glennreyes/p/my-jekyll-site-project-name/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
                    done in 0.283 seconds.
 Auto-regeneration: disabled. Use --watch to enable.
Configuration file: /Users/glennreyes/p/my-jekyll-site-project-name/_config.yml
       Deprecation: Auto-regeneration can no longer be set from your configuration file(s). Use the --[no-]watch/-w command-line option instead.
    Server address: http://127.0.0.1:4000/
  Server running... press ctrl-c to stop.

Same output when I run: bundle exec jekyll serve --watch bundle exec jekyll serve --w jekyll serve --watch jekyll serve --w

That is my gem list:

*** LOCAL GEMS ***

activesupport (4.2.6)
addressable (2.4.0)
bigdecimal (1.2.8)
bundle (0.0.1)
bundler (1.11.2)
coffee-script (2.4.1)
coffee-script-source (1.10.0)
colorator (0.1)
concurrent-ruby (1.0.1)
did_you_mean (1.0.0)
ethon (0.8.1)
execjs (2.6.0)
faraday (0.9.2)
fastimage (2.0.0)
ffi (1.9.10)
gemoji (2.1.0)
github-pages (75)
github-pages-health-check (1.1.1, 1.1.0)
html-pipeline (2.4.0)
i18n (0.7.0)
io-console (0.4.5)
jekyll (3.0.4)
jekyll-coffeescript (1.0.1)
jekyll-feed (0.5.1)
jekyll-gist (1.4.0)
jekyll-github-metadata (1.11.1)
jekyll-mentions (1.1.2)
jekyll-paginate (1.1.0)
jekyll-redirect-from (0.10.0)
jekyll-sass-converter (1.4.0, 1.3.0)
jekyll-seo-tag (1.3.3)
jekyll-sitemap (0.10.0)
jekyll-textile-converter (0.1.0)
jekyll-watch (1.3.1)
jemoji (0.6.2)
json (1.8.3)
kramdown (1.10.0)
liquid (3.0.6)
listen (3.0.6)
mercenary (0.3.6)
mini_portile2 (2.1.0, 2.0.0)
minitest (5.8.4, 5.8.3)
multipart-post (2.0.0)
net-dns (0.8.0)
net-telnet (0.1.1)
nokogiri (1.6.7.2)
octokit (4.3.0)
octopress-autoprefixer (2.0.0)
power_assert (0.2.7, 0.2.6)
psych (2.0.17)
public_suffix (1.5.3)
rack (1.6.4)
rake (11.1.2, 10.4.2)
rb-fsevent (0.9.7)
rb-inotify (0.9.7)
rdiscount (2.1.8)
rdoc (4.2.2, 4.2.1)
redcarpet (3.3.4, 3.3.3)
RedCloth (4.2.9)
rouge (1.10.1)
safe_yaml (1.0.4)
sass (3.4.22)
sawyer (0.7.0)
sprockets (3.6.0)
sprockets-helpers (1.2.1)
terminal-table (1.5.2)
test-unit (3.1.8, 3.1.5)
thread_safe (0.3.5)
tilt (2.0.2)
typhoeus (1.0.1, 0.8.0)
tzinfo (1.2.2)

Can somebody explain what I am doing wrong?