diff --git a/Gemfile b/Gemfile
index 24e12e0bc..51300610f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -36,7 +36,6 @@ if rails4?
   gem 'rails', '4.0.0'
   gem 'redis-rails', :git => 'git://github.com/SamSaffron/redis-store.git'
   gem 'rails-observers'
-  gem 'protected_attributes'
   gem 'actionpack-action_caching'
   gem 'seed-fu' , github: 'mbleigh/seed-fu'
   gem 'spork-rails', :github => 'sporkrb/spork-rails'
@@ -62,7 +61,7 @@ gem 'redis'
 gem 'hiredis'
 gem 'em-redis'
 
-gem 'active_model_serializers', git: 'https://github.com/rails-api/active_model_serializers.git'
+gem 'active_model_serializers'
 
 # we had issues with latest, stick to the rev till we figure this out
 # PR that makes it all hang together welcome
@@ -120,7 +119,7 @@ gem 'sinatra', require: nil
 gem 'slim'  # required for sidekiq-web
 gem 'therubyracer', require: 'v8'
 gem 'thin', require: false
-gem 'diffy', require: false
+gem 'diffy', '>= 3.0', require: false
 gem 'highline', require: false
 
 # Gem that enables support for plugins. It is required.
diff --git a/Gemfile.lock b/Gemfile.lock
index 296c8ab67..5de745416 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -59,13 +59,6 @@ GIT
   specs:
     email_reply_parser (0.6)
 
-GIT
-  remote: https://github.com/rails-api/active_model_serializers.git
-  revision: fe84e0ad5268f1439123fd9a1f9fd12e25a54cd3
-  specs:
-    active_model_serializers (0.8.1)
-      activemodel (>= 3.0)
-
 GIT
   remote: https://github.com/zhangyuan/vestal_versions
   revision: 0ea75ec4e269b5a9e609639919ade0f36381a446
@@ -114,6 +107,8 @@ GEM
     active_attr (0.7.0)
       activemodel (>= 3.0.2, < 4.1)
       activesupport (>= 3.0.2, < 4.1)
+    active_model_serializers (0.8.1)
+      activemodel (>= 3.0)
     activemodel (3.2.12)
       activesupport (= 3.2.12)
       builder (~> 3.0.0)
@@ -161,7 +156,7 @@ GEM
     daemons (1.1.9)
     debug_inspector (0.0.2)
     diff-lcs (1.2.4)
-    diffy (2.1.4)
+    diffy (3.0.1)
     em-redis (0.3.0)
       eventmachine
     ember-rails (0.10.0)
@@ -467,7 +462,7 @@ PLATFORMS
 
 DEPENDENCIES
   active_attr
-  active_model_serializers!
+  active_model_serializers
   activerecord-postgres-hstore
   airbrake (= 3.1.2)
   annotate!
@@ -476,7 +471,7 @@ DEPENDENCIES
   binding_of_caller
   certified
   clockwork
-  diffy
+  diffy (>= 3.0)
   discourse_emoji!
   discourse_plugin!
   em-redis
diff --git a/Gemfile_rails4.lock b/Gemfile_rails4.lock
index 3afaed13f..0308fcbc6 100644
--- a/Gemfile_rails4.lock
+++ b/Gemfile_rails4.lock
@@ -89,13 +89,6 @@ GIT
   specs:
     email_reply_parser (0.6)
 
-GIT
-  remote: https://github.com/rails-api/active_model_serializers.git
-  revision: 8ac4bf90067eef442a6208848f86e55892d724f1
-  specs:
-    active_model_serializers (0.8.1)
-      activemodel (>= 3.2)
-
 GIT
   remote: https://github.com/zhangyuan/vestal_versions
   revision: 0ea75ec4e269b5a9e609639919ade0f36381a446
@@ -139,6 +132,8 @@ GEM
       rack-test (~> 0.6.2)
     actionpack-action_caching (1.0.0)
       actionpack (>= 4.0.0.beta, < 5.0)
+    active_model_serializers (0.8.1)
+      activemodel (>= 3.0)
     activemodel (4.0.0)
       activesupport (= 4.0.0)
       builder (~> 3.1.0)
@@ -318,8 +313,6 @@ GEM
     pg (0.15.1)
     polyglot (0.3.3)
     progress (2.4.0)
-    protected_attributes (1.0.3)
-      activemodel (>= 4.0.0, < 5.0)
     pry (0.9.12.2)
       coderay (~> 1.0.5)
       method_source (~> 0.8)
@@ -477,7 +470,7 @@ PLATFORMS
 
 DEPENDENCIES
   actionpack-action_caching
-  active_model_serializers!
+  active_model_serializers
   airbrake (= 3.1.2)
   annotate!
   barber
@@ -485,7 +478,7 @@ DEPENDENCIES
   binding_of_caller
   certified
   clockwork
-  diffy
+  diffy (>= 3.0)
   discourse_emoji!
   discourse_plugin!
   em-redis
@@ -525,7 +518,6 @@ DEPENDENCIES
   omniauth-twitter
   openid-redis-store
   pg
-  protected_attributes
   pry-nav
   pry-rails
   qunit-rails
diff --git a/app/models/discourse_version_check.rb b/app/models/discourse_version_check.rb
index 8cf79a96b..00e21d04f 100644
--- a/app/models/discourse_version_check.rb
+++ b/app/models/discourse_version_check.rb
@@ -9,8 +9,9 @@ class DiscourseVersionCheck
 
   attr_accessor :latest_version, :critical_updates, :installed_version, :installed_sha, :missing_versions_count, :updated_at
 
-  def active_model_serializer
-    DiscourseVersionCheckSerializer
+  unless rails4?
+    def active_model_serializer
+      DiscourseVersionCheckSerializer
+    end
   end
-
 end
\ No newline at end of file
diff --git a/app/models/topic.rb b/app/models/topic.rb
index 56f9f6bbb..090ce6750 100644
--- a/app/models/topic.rb
+++ b/app/models/topic.rb
@@ -468,7 +468,7 @@ class Topic < ActiveRecord::Base
 
   # Chooses which topic users to feature
   def feature_topic_users(args={})
-    reload
+    reload unless rails4?
 
     # Don't include the OP or the last poster
     to_feature = posts.where('user_id NOT IN (?, ?)', user_id, last_post_user_id)
diff --git a/lib/diff_engine.rb b/lib/diff_engine.rb
index bbcd5e573..4de246c35 100644
--- a/lib/diff_engine.rb
+++ b/lib/diff_engine.rb
@@ -13,7 +13,7 @@ class DiffEngine
   #
   #  returns: html containing decorations indicating the changes
   def self.html_diff(html_before, html_after)
-    Diffy::Diff.new(html_before, html_after).to_s(:html)
+    Diffy::Diff.new(html_before, html_after, {allow_empty_diff: false}).to_s(:html)
   end
 
   # same as html diff, except that it operates on markdown
diff --git a/lib/trashable.rb b/lib/trashable.rb
index 37580e4d3..ef6fd7243 100644
--- a/lib/trashable.rb
+++ b/lib/trashable.rb
@@ -15,13 +15,21 @@ module Trashable
       #
       # with this in place Post.limit(10).with_deleted, will work as expected
       #
-      scope = self.scoped.with_default_scope
+      if rails4?
+        scope = self.all.with_default_scope
+      else
+        scope = self.scoped.with_default_scope
+      end
       scope.where_values.delete(with_deleted_scope_sql)
       scope
     end
 
     def with_deleted_scope_sql
-      scoped.table[:deleted_at].eq(nil).to_sql
+      if rails4?
+        all.table[:deleted_at].eq(nil).to_sql
+      else
+        scoped.table[:deleted_at].eq(nil).to_sql
+      end
     end
   end
 
diff --git a/spec/controllers/static_controller_spec.rb b/spec/controllers/static_controller_spec.rb
index c97c0c233..cad411e07 100644
--- a/spec/controllers/static_controller_spec.rb
+++ b/spec/controllers/static_controller_spec.rb
@@ -13,7 +13,11 @@ describe StaticController do
     end
 
     it "renders the file" do
-      response.should render_template('faq')
+      if rails4?
+        response.should render_template('static/faq.en')
+      else
+        response.should render_template('faq')
+      end
     end
   end
 
@@ -23,7 +27,11 @@ describe StaticController do
 
       context "when #{setting_name} site setting is NOT set" do
         it "renders the #{id} page" do
-          expect(subject).to render_template(id)
+          if rails4?
+            expect(subject).to render_template("static/#{id}.en")
+          else
+            expect(subject).to render_template(id)
+          end
         end
       end
 
diff --git a/spec/models/post_mover_spec.rb b/spec/models/post_mover_spec.rb
index 08deeb789..605e2b24a 100644
--- a/spec/models/post_mover_spec.rb
+++ b/spec/models/post_mover_spec.rb
@@ -147,6 +147,7 @@ describe PostMover do
 
         it "copies the OP, doesn't delete it" do
           new_topic.should be_present
+          new_topic.posts.reload
           new_topic.posts.first.raw.should == p1.raw
 
           new_topic.reload
diff --git a/spec/models/topic_spec.rb b/spec/models/topic_spec.rb
index fd0799245..3f2cb5147 100644
--- a/spec/models/topic_spec.rb
+++ b/spec/models/topic_spec.rb
@@ -661,7 +661,7 @@ describe Topic do
   end
 
   describe 'meta data' do
-    let(:topic) { Fabricate(:topic, meta_data: {hello: 'world'}) }
+    let(:topic) { Fabricate(:topic, meta_data: {'hello' => 'world'}) }
 
     it 'allows us to create a topic with meta data' do
       topic.meta_data['hello'].should == 'world'
@@ -671,7 +671,7 @@ describe Topic do
 
       context 'existing key' do
         before do
-          topic.update_meta_data(hello: 'bane')
+          topic.update_meta_data('hello' => 'bane')
         end
 
         it 'updates the key' do
@@ -681,7 +681,7 @@ describe Topic do
 
       context 'new key' do
         before do
-          topic.update_meta_data(city: 'gotham')
+          topic.update_meta_data('city' => 'gotham')
         end
 
         it 'adds the new key' do