diff --git a/Gemfile.lock b/Gemfile.lock
index 7078d544cbb50..a45fa1029285b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,6 +2,7 @@ PATH
   remote: .
   specs:
     activefile (0.1)
+      actionpack (>= 5.1)
       activejob (>= 5.1)
       activerecord (>= 5.1)
       activesupport (>= 5.1)
@@ -9,6 +10,19 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    actionpack (5.1.1)
+      actionview (= 5.1.1)
+      activesupport (= 5.1.1)
+      rack (~> 2.0)
+      rack-test (~> 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.0.2)
+    actionview (5.1.1)
+      activesupport (= 5.1.1)
+      builder (~> 3.1)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.0.3)
     activejob (5.1.1)
       activesupport (= 5.1.1)
       globalid (>= 0.3.6)
@@ -34,11 +48,13 @@ GEM
     aws-sdk-resources (2.10.7)
       aws-sdk-core (= 2.10.7)
     aws-sigv4 (1.0.0)
+    builder (3.2.3)
     byebug (9.0.6)
     concurrent-ruby (1.0.5)
     declarative (0.0.9)
     declarative-option (0.1.0)
     digest-crc (0.4.1)
+    erubi (1.6.0)
     faraday (0.12.1)
       multipart-post (>= 1.2, < 3)
     globalid (0.4.0)
@@ -161,15 +177,28 @@ GEM
     logging (2.2.2)
       little-plugger (~> 1.1)
       multi_json (~> 1.10)
+    loofah (2.0.3)
+      nokogiri (>= 1.5.9)
     memoist (0.16.0)
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
+    mini_portile2 (2.1.0)
     minitest (5.10.2)
     multi_json (1.12.1)
     multipart-post (2.0.0)
+    nokogiri (1.7.2)
+      mini_portile2 (~> 2.1.0)
     os (0.9.6)
     public_suffix (2.0.5)
+    rack (2.0.3)
+    rack-test (0.6.3)
+      rack (>= 1.0)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.0.3)
+      loofah (~> 2.0)
     rake (12.0.0)
     representable (3.0.4)
       declarative (< 0.1.0)
diff --git a/activefile.gemspec b/activefile.gemspec
index e05421102df2a..cc338087808f3 100644
--- a/activefile.gemspec
+++ b/activefile.gemspec
@@ -11,6 +11,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency "activesupport", ">= 5.1"
   s.add_dependency "activerecord", ">= 5.1"
+  s.add_dependency "actionpack", ">= 5.1"
   s.add_dependency "activejob", ">= 5.1"
 
   s.add_development_dependency "bundler", "~> 1.15"
diff --git a/lib/active_file/disk_controller.rb b/lib/active_file/disk_controller.rb
index 5140c91f0a992..d778cf066f664 100644
--- a/lib/active_file/disk_controller.rb
+++ b/lib/active_file/disk_controller.rb
@@ -1,8 +1,17 @@
+require "action_controller"
+require "active_file/blob"
+require "active_file/verified_key_with_expiration"
+
+require "active_support/core_ext/object/inclusion"
+
 class ActiveFile::DiskController < ActionController::Base
   def show
     if key = decode_verified_key
       blob = ActiveFile::Blob.find_by!(key: key)
-      send_data blob.download, filename: blob.filename, type: blob.content_type, disposition: disposition_param
+      
+      if stale?(etag: blob.checksum)
+        send_data blob.download, filename: blob.filename, type: blob.content_type, disposition: disposition_param
+      end
     else
       head :not_found
     end
@@ -10,7 +19,7 @@ def show
 
   private
     def decode_verified_key
-      ActiveFile::Site::DiskSite::VerifiedKeyWithExpiration.decode(params[:encoded_key])
+      ActiveFile::VerifiedKeyWithExpiration.decode(params[:encoded_key])
     end
 
     def disposition_param
diff --git a/lib/active_file/site/disk_site.rb b/lib/active_file/site/disk_site.rb
index ec60175bbfa83..7916a642c0391 100644
--- a/lib/active_file/site/disk_site.rb
+++ b/lib/active_file/site/disk_site.rb
@@ -40,7 +40,7 @@ def exist?(key)
   def url(key, expires_in:, disposition:, filename:)
     verified_key_with_expiration = ActiveFile::VerifiedKeyWithExpiration.encode(key, expires_in: expires_in)
 
-    if defined?(Rails)
+    if defined?(Rails) && defined?(Rails.application)
       Rails.application.routes.url_helpers.rails_disk_blob_path(verified_key_with_expiration, disposition: disposition)
     else
       "/rails/blobs/#{verified_key_with_expiration}?disposition=#{disposition}"
diff --git a/test/disk_controller_test.rb b/test/disk_controller_test.rb
new file mode 100644
index 0000000000000..ee172b23f781b
--- /dev/null
+++ b/test/disk_controller_test.rb
@@ -0,0 +1,34 @@
+require "test_helper"
+require "database/setup"
+
+require "action_controller"
+require "action_controller/test_case"
+
+require "active_file/disk_controller"
+require "active_file/verified_key_with_expiration"
+
+class ActiveFile::DiskControllerTest < ActionController::TestCase
+  Routes = ActionDispatch::Routing::RouteSet.new.tap do |routes|
+    routes.draw do
+      get "/rails/blobs/:encoded_key" => "active_file/disk#show", as: :rails_disk_blob
+    end
+  end
+
+  setup do
+    @blob = create_blob
+    @routes = Routes
+    @controller = ActiveFile::DiskController.new
+  end
+
+  test "showing blob inline" do
+    get :show, params: { encoded_key: ActiveFile::VerifiedKeyWithExpiration.encode(@blob.key, expires_in: 5.minutes) }
+    assert_equal "inline; filename=\"#{@blob.filename}\"", @response.headers["Content-Disposition"]
+    assert_equal "text/plain", @response.headers["Content-Type"]
+  end
+
+  test "sending blob as attachment" do
+    get :show, params: { encoded_key: ActiveFile::VerifiedKeyWithExpiration.encode(@blob.key, expires_in: 5.minutes), disposition: :attachment }
+    assert_equal "attachment; filename=\"#{@blob.filename}\"", @response.headers["Content-Disposition"]
+    assert_equal "text/plain", @response.headers["Content-Type"]
+  end
+end