diff --git a/railties/lib/rails/rack/static.rb b/railties/lib/rails/rack/static.rb
index ef4e2642e2..f07c6beb5e 100644
--- a/railties/lib/rails/rack/static.rb
+++ b/railties/lib/rails/rack/static.rb
@@ -13,14 +13,18 @@ module Rails
       def call(env)
         path        = env['PATH_INFO'].chomp('/')
         method      = env['REQUEST_METHOD']
-        cached_path = (path.empty? ? 'index' : path) + ::ActionController::Base.page_cache_extension
 
         if FILE_METHODS.include?(method)
           if file_exist?(path)
             return @file_server.call(env)
-          elsif file_exist?(cached_path)
-            env['PATH_INFO'] = cached_path
-            return @file_server.call(env)
+          else
+            cached_path = directory_exist?(path) ? "#{path}/index" : path
+            cached_path += ::ActionController::Base.page_cache_extension
+
+            if file_exist?(cached_path)
+              env['PATH_INFO'] = cached_path
+              return @file_server.call(env)
+            end
           end
         end
 
@@ -32,6 +36,11 @@ module Rails
           full_path = File.join(@file_server.root, ::Rack::Utils.unescape(path))
           File.file?(full_path) && File.readable?(full_path)
         end
+
+        def directory_exist?(path)
+          full_path = File.join(@file_server.root, ::Rack::Utils.unescape(path))
+          File.directory?(full_path) && File.readable?(full_path)
+        end
     end
   end
 end
diff --git a/railties/test/public/foo/bar.html b/railties/test/public/foo/bar.html
new file mode 100644
index 0000000000..9a35646205
--- /dev/null
+++ b/railties/test/public/foo/bar.html
@@ -0,0 +1 @@
+/foo/bar.html
\ No newline at end of file
diff --git a/railties/test/public/foo/index.html b/railties/test/public/foo/index.html
new file mode 100644
index 0000000000..497a2e898f
--- /dev/null
+++ b/railties/test/public/foo/index.html
@@ -0,0 +1 @@
+/foo/index.html
\ No newline at end of file
diff --git a/railties/test/public/index.html b/railties/test/public/index.html
new file mode 100644
index 0000000000..525950ba6b
--- /dev/null
+++ b/railties/test/public/index.html
@@ -0,0 +1 @@
+/index.html
\ No newline at end of file
diff --git a/railties/test/rack_static_test.rb b/railties/test/rack_static_test.rb
new file mode 100644
index 0000000000..5449751002
--- /dev/null
+++ b/railties/test/rack_static_test.rb
@@ -0,0 +1,38 @@
+require 'abstract_unit'
+
+require 'action_controller'
+require 'rails/rack'
+
+class RackStaticTest < ActiveSupport::TestCase
+  DummyApp = lambda { |env|
+    [200, {"Content-Type" => "text/plain"}, ["Hello, World!"]]
+  }
+  App = Rails::Rack::Static.new(DummyApp)
+
+  test "serves dynamic content" do
+    assert_equal "Hello, World!", get("/nofile")
+  end
+
+  test "serves static index at root" do
+    assert_equal "/index.html", get("/index.html")
+    assert_equal "/index.html", get("/index")
+    assert_equal "/index.html", get("/")
+  end
+
+  test "serves static file in directory" do
+    assert_equal "/foo/bar.html", get("/foo/bar.html")
+    assert_equal "/foo/bar.html", get("/foo/bar/")
+    assert_equal "/foo/bar.html", get("/foo/bar")
+  end
+
+  test "serves static index file in directory" do
+    assert_equal "/foo/index.html", get("/foo/index.html")
+    assert_equal "/foo/index.html", get("/foo/")
+    assert_equal "/foo/index.html", get("/foo")
+  end
+
+  private
+    def get(path)
+      Rack::MockRequest.new(App).request("GET", path).body
+    end
+end