diff --git a/.ruby-version b/.ruby-version
index 45674f16..9183195a 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-2.3.3
\ No newline at end of file
+2.4.0
\ No newline at end of file
diff --git a/Dockerfile b/Dockerfile
index b5cdfdad..d6ce12b7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 
-FROM ruby:2.3.3
+FROM ruby:2.4.0
 MAINTAINER Conor Heine <conor.heine@gmail.com>
 
 RUN apt-get update
diff --git a/Gemfile b/Gemfile
index 0263f4e6..59d1af66 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,10 +1,10 @@
 source 'https://rubygems.org'
-ruby '2.3.3'
+ruby '2.4.0'
 
 gem 'rake'
 gem 'thor'
 gem 'pry', '~> 0.10.0'
-gem 'activesupport', '~> 4.2', require: false
+gem 'activesupport', '~> 5.0', require: false
 gem 'yajl-ruby', require: false
 
 group :app do
diff --git a/Gemfile.lock b/Gemfile.lock
index 2fc962fc..730d8328 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,11 +1,10 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (4.2.7.1)
+    activesupport (5.0.1)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (~> 0.7)
-      json (~> 1.7, >= 1.7.7)
       minitest (~> 5.1)
-      thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
     backports (3.6.8)
     better_errors (2.1.1)
@@ -17,26 +16,25 @@ GEM
     coffee-script (2.4.1)
       coffee-script-source
       execjs
-    coffee-script-source (1.11.1)
-    concurrent-ruby (1.0.2)
+    coffee-script-source (1.12.2)
+    concurrent-ruby (1.0.4)
     daemons (1.2.4)
     erubis (2.7.0)
-    ethon (0.9.1)
+    ethon (0.10.1)
       ffi (>= 1.3.0)
     eventmachine (1.2.1)
     execjs (2.7.0)
-    ffi (1.9.14)
+    ffi (1.9.17)
     highline (1.7.8)
-    html-pipeline (2.4.2)
+    html-pipeline (2.5.0)
       activesupport (>= 2)
       nokogiri (>= 1.4)
     i18n (0.7.0)
-    json (1.8.3)
     method_source (0.8.2)
     mini_portile2 (2.1.0)
-    minitest (5.9.1)
+    minitest (5.10.1)
     multi_json (1.12.1)
-    nokogiri (1.6.8.1)
+    nokogiri (1.7.0.1)
       mini_portile2 (~> 2.1.0)
     options (2.3.2)
     progress_bar (1.1.0)
@@ -51,9 +49,9 @@ GEM
       rack
     rack-test (0.6.3)
       rack (>= 1.0)
-    rake (11.3.0)
+    rake (12.0.0)
     rr (1.2.0)
-    sass (3.4.22)
+    sass (3.4.23)
     sinatra (1.4.7)
       rack (~> 1.5)
       rack-protection (~> 1.4)
@@ -66,7 +64,7 @@ GEM
       sinatra (~> 1.4.0)
       tilt (>= 1.3, < 3)
     slop (3.6.0)
-    sprockets (3.7.0)
+    sprockets (3.7.1)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-helpers (1.2.1)
@@ -75,24 +73,26 @@ GEM
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)
-    thor (0.19.3)
+    thor (0.19.4)
     thread_safe (0.3.5)
     tilt (2.0.5)
-    tty-pager (0.4.0)
+    tty-pager (0.5.0)
       tty-screen (~> 0.5.0)
-      tty-which (~> 0.1.0)
-      verse (~> 0.4.0)
+      tty-which (~> 0.2.0)
+      verse (~> 0.5.0)
     tty-screen (0.5.0)
-    tty-which (0.1.0)
-    typhoeus (1.1.0)
+    tty-which (0.2.1)
+    typhoeus (1.1.2)
       ethon (>= 0.9.0)
     tzinfo (1.2.2)
       thread_safe (~> 0.1)
-    uglifier (3.0.3)
+    uglifier (3.0.4)
       execjs (>= 0.3.0, < 3)
+    unicode-display_width (1.1.3)
     unicode_utils (1.4.0)
     unix_utils (0.0.15)
-    verse (0.4.0)
+    verse (0.5.0)
+      unicode-display_width (~> 1.1.0)
       unicode_utils (~> 1.4.0)
     yajl-ruby (1.3.0)
 
@@ -100,7 +100,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  activesupport (~> 4.2)
+  activesupport (~> 5.0)
   better_errors
   browser
   coffee-script
@@ -128,7 +128,7 @@ DEPENDENCIES
   yajl-ruby
 
 RUBY VERSION
-   ruby 2.3.3p222
+   ruby 2.4.0p0
 
 BUNDLED WITH
-   1.13.6
+   1.14.1
diff --git a/README.md b/README.md
index 8d41f125..06f27841 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ Unless you wish to contribute to the project, I recommend using the hosted versi
 
 DevDocs is made of two pieces: a Ruby scraper that generates the documentation and metadata, and a JavaScript app powered by a small Sinatra app.
 
-DevDocs requires Ruby 2.3.3, libcurl, and a JavaScript runtime supported by [ExecJS](https://github.com/rails/execjs#readme) (included in OS X and Windows; [Node.js](https://nodejs.org/en/) on Linux). Once you have these installed, run the following commands:
+DevDocs requires Ruby 2.4.0, libcurl, and a JavaScript runtime supported by [ExecJS](https://github.com/rails/execjs#readme) (included in OS X and Windows; [Node.js](https://nodejs.org/en/) on Linux). Once you have these installed, run the following commands:
 
 ```
 git clone https://github.com/Thibaut/devdocs.git && cd devdocs
diff --git a/lib/app.rb b/lib/app.rb
index 66c0001a..a93d980b 100644
--- a/lib/app.rb
+++ b/lib/app.rb
@@ -7,6 +7,7 @@ class App < Sinatra::Application
   Bundler.require environment
   require 'sinatra/cookies'
   require 'tilt/erubis'
+  require 'active_support/notifications'
 
   Rack::Mime::MIME_TYPES['.webapp'] = 'application/x-web-app-manifest+json'
 
diff --git a/test/lib/docs/core/url_test.rb b/test/lib/docs/core/url_test.rb
index 8dd187c5..08839b54 100644
--- a/test/lib/docs/core/url_test.rb
+++ b/test/lib/docs/core/url_test.rb
@@ -197,7 +197,7 @@ class DocsUrlTest < MiniTest::Spec
       end
 
       it "returns nil with 'http://example.com'" do
-        assert_equal nil, url.subpath_to('http://example.com')
+        assert_nil url.subpath_to('http://example.com')
       end
     end