diff --git a/README.md b/README.md
index 0069260f..b4003127 100644
--- a/README.md
+++ b/README.md
@@ -532,6 +532,10 @@ Your Rack middleware can pass author details to Gollum in a Hash in the session
 ## WINDOWS FILENAME VALIDATION
 Note that filenames on windows must not contain any of the following characters `\ / : * ? " < > |`. See [this support article](http://support.microsoft.com/kb/177506) for details.
 
+## CONFIG FILE
+
+Gollum optionaly takes a `--config file`. See [config.rb](https://github.com/github/gollum/blob/master/config.rb) for an example.
+
 ## CONTRIBUTE
 
 If you'd like to hack on Gollum, start by forking my repo on GitHub:
diff --git a/config.rb b/config.rb
new file mode 100644
index 00000000..3f28df94
--- /dev/null
+++ b/config.rb
@@ -0,0 +1,28 @@
+# Example gollum config
+# gollum ../wiki --config config.rb
+#
+# or run from source with
+#
+# bundle exec bin/gollum ../wiki/ --config config.rb
+
+# Remove const to avoid
+# warning: already initialized constant FORMAT_NAMES
+#
+# only remove if it's defined.
+# constant Gollum::Page::FORMAT_NAMES not defined (NameError)
+Gollum::Page.send :remove_const, :FORMAT_NAMES if defined? Gollum::Page::FORMAT_NAMES
+# limit to one format
+Gollum::Page::FORMAT_NAMES = { :markdown  => "Markdown" }
+
+=begin
+Valid formats are:
+{ :markdown  => "Markdown",
+  :textile   => "Textile",
+  :rdoc      => "RDoc",
+  :org       => "Org-mode",
+  :creole    => "Creole",
+  :rest      => "reStructuredText",
+  :asciidoc  => "AsciiDoc",
+  :mediawiki => "MediaWiki",
+  :pod       => "Pod" }
+=end