diff --git a/lib/yard/code_objects/extra_file_object.rb b/lib/yard/code_objects/extra_file_object.rb
index c0f53a3e5..1de75bd6b 100644
--- a/lib/yard/code_objects/extra_file_object.rb
+++ b/lib/yard/code_objects/extra_file_object.rb
@@ -61,6 +61,10 @@ def inspect
 
     def type; :extra_file end
 
+    def source_type; :ruby end
+
+    def parent; YARD::Registry.root end
+
     def ==(other)
       return false unless self.class === other
       other.filename == filename
diff --git a/lib/yard/code_objects/root_extra_file_object.rb b/lib/yard/code_objects/root_extra_file_object.rb
new file mode 100644
index 000000000..e69de29bb
diff --git a/lib/yard/serializers/file_system_serializer.rb b/lib/yard/serializers/file_system_serializer.rb
index c95f585f1..bed1a1af4 100644
--- a/lib/yard/serializers/file_system_serializer.rb
+++ b/lib/yard/serializers/file_system_serializer.rb
@@ -51,7 +51,7 @@ def serialized_path(object)
         return object if object.is_a?(String)
 
         if object.is_a?(CodeObjects::ExtraFileObject)
-          fspath = ['file.' + object.name + (extension.empty? ? '' : ".#{extension}")]
+          fspath = ['_file', object.name + (extension.empty? ? '' : ".#{extension}")]
         else
           objname = object != YARD::Registry.root ? mapped_name(object) : "top-level-namespace"
           objname += '_' + object.scope.to_s[0, 1] if object.is_a?(CodeObjects::MethodObject)
diff --git a/lib/yard/server/doc_server_serializer.rb b/lib/yard/server/doc_server_serializer.rb
index 131cda807..5263cf8c4 100644
--- a/lib/yard/server/doc_server_serializer.rb
+++ b/lib/yard/server/doc_server_serializer.rb
@@ -20,7 +20,7 @@ def serialized_path(object)
         when CodeObjects::ConstantObject, CodeObjects::ClassVariableObject
           serialized_path(object.namespace) + "##{object.name}-#{object.type}"
         when CodeObjects::ExtraFileObject
-          super(object).gsub(/^file\./, 'file/')
+          super(object).gsub(/^_file\//, 'file/')
         else
           super(object)
         end
diff --git a/spec/serializers/file_system_serializer_spec.rb b/spec/serializers/file_system_serializer_spec.rb
index 0068549e4..28c308fb3 100644
--- a/spec/serializers/file_system_serializer_spec.rb
+++ b/spec/serializers/file_system_serializer_spec.rb
@@ -66,7 +66,7 @@
     it "handles ExtraFileObject's" do
       s = Serializers::FileSystemSerializer.new
       e = CodeObjects::ExtraFileObject.new('filename.txt', '')
-      expect(s.serialized_path(e)).to eq 'file.filename.html'
+      expect(s.serialized_path(e)).to eq '_file/filename.html'
     end
 
     it "differentiates instance and class methods from serialized path" do
diff --git a/spec/templates/helpers/html_helper_spec.rb b/spec/templates/helpers/html_helper_spec.rb
index 6b02c6e93..aa17d4509 100644
--- a/spec/templates/helpers/html_helper_spec.rb
+++ b/spec/templates/helpers/html_helper_spec.rb
@@ -415,12 +415,12 @@ def parse_link(link)
       expect(parse_link(resolve_links("{file:TEST.txt#abc}"))).to eq(
         :inner_text => "TEST",
         :title => "TEST",
-        :href => "file.TEST.html#abc"
+        :href => "_file/TEST.html#abc"
       )
       expect(parse_link(resolve_links("{file:TEST.txt title}"))).to eq(
         :inner_text => "title",
         :title => "title",
-        :href => "file.TEST.html"
+        :href => "_file/TEST.html"
       )
     end
 
diff --git a/templates/default/fulldoc/html/setup.rb b/templates/default/fulldoc/html/setup.rb
index 201ba63c5..3df5ea8a7 100644
--- a/templates/default/fulldoc/html/setup.rb
+++ b/templates/default/fulldoc/html/setup.rb
@@ -8,7 +8,7 @@ def init
   generate_assets
   serialize('_index.html')
   options.files.each_with_index do |file, _i|
-    serialize_file(file, file.title)
+    serialize_file(file)
   end
 
   options.delete(:objects)
@@ -48,6 +48,7 @@ def serialize_onefile
 # Generate the index document for the output
 # @params [Hash] options contains data and flags that influence the output
 def serialize_index(options)
+  options.object = Registry.root
   Templates::Engine.with_serializer('index.html', options.serializer) do
     T('layout').run(options.merge(:index => true))
   end
@@ -57,18 +58,12 @@ def serialize_index(options)
 # the README file or files specified on the command-line.
 #
 # @param [File] file object to be saved to the output
-# @param [String] title currently unused
 #
 # @see layout#diskfile
-def serialize_file(file, title = nil) # rubocop:disable Lint/UnusedMethodArgument
-  options.object = Registry.root
+def serialize_file(file)
   options.file = file
-  outfile = 'file.' + file.name + '.html'
-
   serialize_index(options) if file == options.readme
-  Templates::Engine.with_serializer(outfile, options.serializer) do
-    T('layout').run(options)
-  end
+  serialize(file)
   options.delete(:file)
 end
 
diff --git a/templates/guide/fulldoc/html/setup.rb b/templates/guide/fulldoc/html/setup.rb
index 87d4b121b..2ff61ec77 100644
--- a/templates/guide/fulldoc/html/setup.rb
+++ b/templates/guide/fulldoc/html/setup.rb
@@ -23,7 +23,7 @@ def init
   class << options.serializer
     define_method(:serialized_path) do |object|
       if CodeObjects::ExtraFileObject === object
-        super(object).sub(/^file\./, '').downcase
+        super(object).sub(/^_file\//, '').downcase
       else
         super(object)
       end