diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66aa5cb6..98866c59 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 ### Unreleased
 
+*   Don't serve up assets without digests in development.
+
+    If `config.assets.digest = true` and `config.assets.raise_runtime_errors = true`,
+    serve an asset only if the request has a digest.
+
+    *Dan Kang*
+
 *   Fix issues related `config.assets.manifest` option, including issues with `assets:precompile` Rake task.
 
     *Johnny Shields*
diff --git a/README.md b/README.md
index e6bde0ff..6f3d7a63 100644
--- a/README.md
+++ b/README.md
@@ -89,7 +89,9 @@ Defines the full path to be used for the asset precompiler's manifest file. Defa
 
 **`config.assets.digest`**
 
-Link to undigest asset filenames. This option will eventually go away. Unless when `compile` is disabled.
+When enabled, fingerprints will be added to asset filenames.
+If `config.assets.raise_runtime_errors` is also enabled, requests for assets
+will require fingerprints.
 
 **`config.assets.debug`**
 
diff --git a/lib/sprockets/rails/environment.rb b/lib/sprockets/rails/environment.rb
new file mode 100644
index 00000000..29e1cf45
--- /dev/null
+++ b/lib/sprockets/rails/environment.rb
@@ -0,0 +1,39 @@
+require 'sprockets'
+require 'sprockets/rails/helper'
+
+module Sprockets
+  module Rails
+    class Environment < Sprockets::Environment
+      class NoDigestError < StandardError
+        def initialize(asset)
+          msg = "Assets should not be requested directly without their digests: " <<
+                "Use the helpers in ActionView::Helpers to request #{asset}"
+          super(msg)
+        end
+      end
+
+      def call(env)
+        if Sprockets::Rails::Helper.raise_runtime_errors && context_class.digest_assets
+          path = unescape(env['PATH_INFO'].to_s.sub(/^\//, ''))
+
+          if fingerprint = path_fingerprint(path)
+            path = path.sub("-#{fingerprint}", '')
+          else
+            raise NoDigestError.new(path)
+          end
+
+          asset = find_asset(path)
+          if asset && asset.digest != fingerprint
+            asset_path = File.join(context_class.assets_prefix || "/", asset.digest_path)
+            asset_path += '?' + env['QUERY_STRING'] if env['QUERY_STRING']
+            [302, {"Location" => asset_path}, []]
+          else
+            super(env)
+          end
+        else
+          super(env)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/sprockets/railtie.rb b/lib/sprockets/railtie.rb
index 1c5448b2..205a34eb 100644
--- a/lib/sprockets/railtie.rb
+++ b/lib/sprockets/railtie.rb
@@ -3,6 +3,7 @@
 require 'action_controller/railtie'
 require 'active_support/core_ext/module/remove_method'
 require 'sprockets'
+require 'sprockets/rails/environment'
 require 'sprockets/rails/helper'
 require 'sprockets/rails/version'
 
@@ -18,9 +19,9 @@ class Configuration
     remove_possible_method :assets
     remove_possible_method :assets=
 
-    # Returns Sprockets::Environment for app config.
+    # Returns Sprockets::Rails::Environment for app config.
     def assets
-      @assets ||= Sprockets::Environment.new(root.to_s) do |env|
+      @assets ||= Sprockets::Rails::Environment.new(root.to_s) do |env|
         env.version = ::Rails.env
 
         path = "#{config.root}/tmp/cache/assets/#{::Rails.env}"
diff --git a/test/test_environment.rb b/test/test_environment.rb
new file mode 100644
index 00000000..34e417e5
--- /dev/null
+++ b/test/test_environment.rb
@@ -0,0 +1,114 @@
+require 'minitest/autorun'
+
+require 'rack/test'
+require 'sprockets/rails/environment'
+require 'sprockets/rails/helper'
+
+Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
+
+class EnvironmentTest < Minitest::Test
+  include Rack::Test::Methods
+
+  FIXTURES_PATH = File.expand_path("../fixtures", __FILE__)
+
+  def setup
+    @assets = Sprockets::Rails::Environment.new
+    @assets.append_path FIXTURES_PATH
+    @assets.context_class.class_eval do
+      include ::Sprockets::Rails::Helper
+    end
+    @assets.context_class.assets_prefix = "/assets"
+    @assets.context_class.digest_assets = true
+
+    @foo_js_digest  = @assets['foo.js'].digest
+
+    Sprockets::Rails::Helper.raise_runtime_errors = true
+  end
+
+  def default_app
+    env = @assets
+
+    Rack::Builder.new do
+      map "/assets" do
+        run env
+      end
+    end
+  end
+
+  def app
+    @app ||= default_app
+  end
+end
+
+class DigestTest < EnvironmentTest
+  def setup
+    super
+    @assets.context_class.digest_assets = true
+  end
+
+  def test_assets_with_digest
+    get "/assets/foo-#{@foo_js_digest}.js"
+    assert_equal 200, last_response.status
+  end
+
+  def test_assets_with_no_digest
+    assert_raises(Sprockets::Rails::Environment::NoDigestError) do
+      get "/assets/foo.js"
+    end
+  end
+
+  def test_assets_with_wrong_digest
+    wrong_digest = "0" * 32
+    get "/assets/foo-#{wrong_digest}.js"
+    assert_equal 302, last_response.status
+
+    follow_redirect!
+    assert_equal "/assets/foo-#{@foo_js_digest}.js", last_request.path
+    assert_equal 200, last_response.status
+  end
+
+  def test_assets_with_wrong_digest_with_query_parameters
+    wrong_digest = "0" * 32
+    get "/assets/foo-#{wrong_digest}.js?body=1"
+    assert_equal 302, last_response.status
+
+    follow_redirect!
+    assert_equal "/assets/foo-#{@foo_js_digest}.js", last_request.path
+    assert_equal "body=1", last_request.query_string
+    assert_equal 200, last_response.status
+  end
+end
+
+class NoDigestTest < EnvironmentTest
+  def setup
+    super
+    @assets.context_class.digest_assets = false
+  end
+
+  def test_assets_with_digest
+    get "/assets/foo-#{@foo_js_digest}.js"
+    assert_equal 200, last_response.status
+  end
+
+  def test_assets_with_no_digest
+    get "/assets/foo.js"
+    assert_equal 200, last_response.status
+  end
+end
+
+class NoRuntimeErrorTest < EnvironmentTest
+  def setup
+    super
+    Sprockets::Rails::Helper.raise_runtime_errors = false
+  end
+
+  def test_assets_with_digest
+    get "/assets/foo-#{@foo_js_digest}.js"
+    assert_equal 200, last_response.status
+  end
+
+  def test_assets_with_no_digest
+    get "/assets/foo.js"
+    assert_equal 200, last_response.status
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index f90ddb36..b3d47314 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -2,6 +2,7 @@
 
 require 'action_view'
 require 'sprockets'
+require 'sprockets/rails/environment'
 require 'sprockets/rails/helper'
 
 Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
@@ -10,7 +11,7 @@ class HelperTest < Minitest::Test
   FIXTURES_PATH = File.expand_path("../fixtures", __FILE__)
 
   def setup
-    assets = @assets = Sprockets::Environment.new
+    assets = @assets = Sprockets::Rails::Environment.new
     @assets.append_path FIXTURES_PATH
     @assets.context_class.class_eval do
       include ::Sprockets::Rails::Helper
diff --git a/test/test_task.rb b/test/test_task.rb
index 49e93192..aacc57d0 100644
--- a/test/test_task.rb
+++ b/test/test_task.rb
@@ -2,6 +2,7 @@
 require 'tmpdir'
 
 require 'sprockets'
+require 'sprockets/rails/environment'
 require 'sprockets/rails/task'
 
 Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)
@@ -13,7 +14,7 @@ def setup
     @rake = Rake::Application.new
     Rake.application = @rake
 
-    @assets = Sprockets::Environment.new
+    @assets = Sprockets::Rails::Environment.new
     @assets.append_path FIXTURES_PATH
 
     @dir = File.join(Dir::tmpdir, 'rails', 'task')