diff --git a/Gemfile b/Gemfile
index a5a58995..cbd97b7b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,7 +5,7 @@ gem "posix-spawn", :platforms => :ruby
 gem "redcarpet", :platforms => :ruby
 gem "kramdown", :platforms => :jruby
 gem "RedCloth"
-gem "commonmarker", "~> 0.14.12"
+gem "commonmarker", "~> 0.18.1"
 gem "rdoc", "~>3.6"
 gem "org-ruby", "= 0.9.9"
 gem "creole", "~>0.3.6"
diff --git a/lib/github/markup.rb b/lib/github/markup.rb
index 84c1e45f..5a78d006 100644
--- a/lib/github/markup.rb
+++ b/lib/github/markup.rb
@@ -20,38 +20,36 @@ module Markups
     MARKUP_RST = :rst
     MARKUP_TEXTILE = :textile
   end
-  
+
   module Markup
     extend self
-    
+
     @@markups = {}
 
     def markups
       @@markups
     end
-    
+
     def markup_impls
       markups.values
     end
 
     def preload!
-      markup_impls.each do |markup|
-        markup.load
-      end
+      markup_impls.each(&:load)
     end
 
-    def render(filename, content, symlink = false)
-      if impl = renderer(filename, content, symlink)
-        impl.render(filename, content)
+    def render(filename, content, symlink: false, options: {})
+      if (impl = renderer(filename, content, symlink: symlink))
+        impl.render(filename, content, options: options)
       else
         content
       end
     end
-    
+
     def render_s(symbol, content)
-      if content.nil?
-        raise ArgumentError, 'Can not render a nil.'
-      elsif markups.has_key?(symbol)
+      raise ArgumentError, 'Can not render a nil.' if content.nil?
+
+      if markups.key?(symbol)
         markups[symbol].render(nil, content)
       else
         content
@@ -59,11 +57,12 @@ def render_s(symbol, content)
     end
 
     def markup(symbol, gem_name, regexp, languages, opts = {}, &block)
-      markup_impl(symbol, GemImplementation.new(regexp, languages, gem_name, &block))
+      impl = GemImplementation.new(regexp, languages, gem_name, &block)
+      markup_impl(symbol, impl)
     end
-    
+
     def markup_impl(symbol, impl)
-      if markups.has_key?(symbol)
+      if markups.key?(symbol)
         raise ArgumentError, "The '#{symbol}' symbol is already defined."
       end
       markups[symbol] = impl
@@ -74,25 +73,26 @@ def command(symbol, command, regexp, languages, name, &block)
         command = file
       end
 
-      markup_impl(symbol, CommandImplementation.new(regexp, languages, command, name, &block))
+      impl = CommandImplementation.new(regexp, languages, command, name, &block)
+      markup_impl(symbol, impl)
     end
 
-    def can_render?(filename, content, symlink = false)
-      !!renderer(filename, content, symlink)
+    def can_render?(filename, content, symlink: false)
+      renderer(filename, content, symlink: symlink) != nil
     end
 
-    def renderer(filename, content, symlink = false)
-      language = language(filename, content, symlink)
-      markup_impls.find { |impl|
+    def renderer(filename, content, symlink: false)
+      language = language(filename, content, symlink: symlink)
+      markup_impls.find do |impl|
         impl.match?(filename, language)
-      }
+      end
     end
 
-    def language(filename, content, symlink = false)
-      if defined?(::Linguist)
-        blob = Linguist::Blob.new(filename, content, symlink: symlink)
-        return Linguist.detect(blob, allow_empty: true)
-      end
+    def language(filename, content, symlink: false)
+      return unless defined?(::Linguist)
+
+      blob = Linguist::Blob.new(filename, content, symlink: symlink)
+      Linguist.detect(blob, allow_empty: true)
     end
 
     # Define markups
diff --git a/lib/github/markup/command_implementation.rb b/lib/github/markup/command_implementation.rb
index ed67113c..4ecf2ad5 100644
--- a/lib/github/markup/command_implementation.rb
+++ b/lib/github/markup/command_implementation.rb
@@ -22,7 +22,7 @@ def initialize(regexp, languages, command, name, &block)
         @name = name
       end
 
-      def render(filename, content)
+      def render(filename, content, options: {})
         rendered = execute(command, content)
         rendered = rendered.to_s.empty? ? content : rendered
         call_block(rendered, content)
diff --git a/lib/github/markup/gem_implementation.rb b/lib/github/markup/gem_implementation.rb
index 29582ce8..843717e6 100644
--- a/lib/github/markup/gem_implementation.rb
+++ b/lib/github/markup/gem_implementation.rb
@@ -12,14 +12,14 @@ def initialize(regexp, languages, gem_name, &renderer)
       end
 
       def load
-        return if @loaded
+        return if defined?(@loaded) && @loaded
         require gem_name
         @loaded = true
       end
 
-      def render(filename, content)
+      def render(filename, content, options: {})
         load
-        renderer.call(filename, content)
+        renderer.call(filename, content, options: options)
       end
 
       def name
diff --git a/lib/github/markup/implementation.rb b/lib/github/markup/implementation.rb
index aaa92534..f2854e22 100644
--- a/lib/github/markup/implementation.rb
+++ b/lib/github/markup/implementation.rb
@@ -16,7 +16,7 @@ def load
         # no-op by default
       end
 
-      def render(filename, content)
+      def render(filename, content, options: {})
         raise NotImplementedError, "subclasses of GitHub::Markup::Implementation must define #render"
       end
 
diff --git a/lib/github/markup/markdown.rb b/lib/github/markup/markdown.rb
index c51476fd..aa012d48 100644
--- a/lib/github/markup/markdown.rb
+++ b/lib/github/markup/markdown.rb
@@ -4,25 +4,26 @@ module GitHub
   module Markup
     class Markdown < Implementation
       MARKDOWN_GEMS = {
-        "commonmarker" => proc { |content|
-          CommonMarker.render_html(content, :GITHUB_PRE_LANG, [:tagfilter, :autolink, :table, :strikethrough])
+        "commonmarker" => proc { |content, options: {}|
+          commonmarker_opts = [:GITHUB_PRE_LANG].concat(options.fetch(:commonmarker_opts, []))
+          CommonMarker.render_html(content, commonmarker_opts, [:tagfilter, :autolink, :table, :strikethrough])
         },
-        "github/markdown" => proc { |content|
+        "github/markdown" => proc { |content, options: {}|
           GitHub::Markdown.render(content)
         },
-        "redcarpet" => proc { |content|
+        "redcarpet" => proc { |content, options: {}|
           Redcarpet::Markdown.new(Redcarpet::Render::HTML).render(content)
         },
-        "rdiscount" => proc { |content|
+        "rdiscount" => proc { |content, options: {}|
           RDiscount.new(content).to_html
         },
-        "maruku" => proc { |content|
+        "maruku" => proc { |content, options: {}|
           Maruku.new(content).to_html
         },
-        "kramdown" => proc { |content|
+        "kramdown" => proc { |content, options: {}|
           Kramdown::Document.new(content).to_html
         },
-        "bluecloth" => proc { |content|
+        "bluecloth" => proc { |content, options: {}|
           BlueCloth.new(content).to_html
         },
       }
@@ -44,9 +45,9 @@ def load
         raise LoadError, "no suitable markdown gem found"
       end
 
-      def render(filename, content)
+      def render(filename, content, options: {})
         load
-        @renderer.call(content)
+        @renderer.call(content, options: options)
       end
 
       def name
diff --git a/lib/github/markup/rdoc.rb b/lib/github/markup/rdoc.rb
index 749618d9..32cb4194 100644
--- a/lib/github/markup/rdoc.rb
+++ b/lib/github/markup/rdoc.rb
@@ -9,7 +9,7 @@ def initialize
         super(/rdoc/, ["RDoc"])
       end
 
-      def render(filename, content)
+      def render(filename, content, options: {})
         if ::RDoc::VERSION.to_i >= 4
           h = ::RDoc::Markup::ToHtml.new(::RDoc::Options.new)
         else
diff --git a/lib/github/markups.rb b/lib/github/markups.rb
index 61138e85..440e0dbf 100644
--- a/lib/github/markups.rb
+++ b/lib/github/markups.rb
@@ -4,30 +4,30 @@
 
 markup_impl(::GitHub::Markups::MARKUP_MARKDOWN, ::GitHub::Markup::Markdown.new)
 
-markup(::GitHub::Markups::MARKUP_TEXTILE, :redcloth, /textile/, ["Textile"]) do |filename, content|
+markup(::GitHub::Markups::MARKUP_TEXTILE, :redcloth, /textile/, ["Textile"]) do |filename, content, options: {}|
   RedCloth.new(content).to_html
 end
 
 markup_impl(::GitHub::Markups::MARKUP_RDOC, GitHub::Markup::RDoc.new)
 
-markup(::GitHub::Markups::MARKUP_ORG, 'org-ruby', /org/, ["Org"]) do |filename, content|
+markup(::GitHub::Markups::MARKUP_ORG, 'org-ruby', /org/, ["Org"]) do |filename, content, options: {}|
   Orgmode::Parser.new(content, {
                         :allow_include_files => false,
                         :skip_syntax_highlight => true
                       }).to_html
 end
 
-markup(::GitHub::Markups::MARKUP_CREOLE, :creole, /creole/, ["Creole"]) do |filename, content|
+markup(::GitHub::Markups::MARKUP_CREOLE, :creole, /creole/, ["Creole"]) do |filename, content, options: {}|
   Creole.creolize(content)
 end
 
-markup(::GitHub::Markups::MARKUP_MEDIAWIKI, :wikicloth, /mediawiki|wiki/, ["MediaWiki"]) do |filename, content|
+markup(::GitHub::Markups::MARKUP_MEDIAWIKI, :wikicloth, /mediawiki|wiki/, ["MediaWiki"]) do |filename, content, options: {}|
   wikicloth = WikiCloth::WikiCloth.new(:data => content)
   WikiCloth::WikiBuffer::HTMLElement::ESCAPED_TAGS << 'tt' unless WikiCloth::WikiBuffer::HTMLElement::ESCAPED_TAGS.include?('tt')
   wikicloth.to_html(:noedit => true)
 end
 
-markup(::GitHub::Markups::MARKUP_ASCIIDOC, :asciidoctor, /adoc|asc(iidoc)?/, ["AsciiDoc"]) do |filename, content|
+markup(::GitHub::Markups::MARKUP_ASCIIDOC, :asciidoctor, /adoc|asc(iidoc)?/, ["AsciiDoc"]) do |filename, content, options: {}|
   attributes = {
     'showtitle' => '@',
     'idprefix' => '',
diff --git a/test/markup_test.rb b/test/markup_test.rb
index b324c1ab..eedaccdf 100644
--- a/test/markup_test.rb
+++ b/test/markup_test.rb
@@ -102,7 +102,7 @@ def test_raises_error_if_command_exits_non_zero
     GitHub::Markup.command(:doesntmatter, 'test/fixtures/fail.sh', /fail/, ['Java'], 'fail')
     assert GitHub::Markup.can_render?('README.java', 'stop swallowing errors')
     begin
-      GitHub::Markup.render('README.java', "stop swallowing errors", false)
+      GitHub::Markup.render('README.java', "stop swallowing errors", symlink: false)
     rescue GitHub::Markup::CommandError => e
       assert_equal "failure message", e.message
     else
@@ -114,4 +114,9 @@ def test_preserve_markup
     content = "Noël"
     assert_equal content.encoding.name, GitHub::Markup.render('Foo.rst', content).encoding.name
   end
+
+  def test_commonmarker_options
+    assert_equal "<p>hello <!-- raw HTML omitted --> world</p>\n", GitHub::Markup.render("test.md", "hello <bad> world")
+    assert_equal "<p>hello <bad> world</p>\n", GitHub::Markup.render("test.md", "hello <bad> world", options: {commonmarker_opts: [:UNSAFE]})
+  end
 end