diff --git a/Gemfile b/Gemfile
index 3b8887ca0..b2da2827d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,8 +5,6 @@ gem "jquery-rails", "~> 2.0.2"
 gem "coderay", "~> 1.1.0"
 gem "fastercsv", "~> 1.5.0", :platforms => [:mri_18, :mingw_18, :jruby]
 gem "builder", "3.0.0"
-# TODO: upgrade to redcarpet 3.x when ruby1.8 support is dropped
-gem "redcarpet", "~> 2.3.0"
 
 # Optional gem for LDAP authentication
 group :ldap do
@@ -19,14 +17,20 @@ group :openid do
   gem "rack-openid"
 end
 
-# Optional gem for exporting the gantt to a PNG file, not supported with jruby
 platforms :mri, :mingw do
+  # Optional gem for exporting the gantt to a PNG file, not supported with jruby
   group :rmagick do
     # RMagick 2 supports ruby 1.9
     # RMagick 1 would be fine for ruby 1.8 but Bundler does not support
     # different requirements for the same gem on different platforms
     gem "rmagick", ">= 2.0.0"
   end
+
+  # Optional Markdown support, not for JRuby
+  group :markdown do
+    # TODO: upgrade to redcarpet 3.x when ruby1.8 support is dropped
+    gem "redcarpet", "~> 2.3.0"
+  end
 end
 
 platforms :jruby do
diff --git a/lib/redmine.rb b/lib/redmine.rb
index 187689ea1..64d63dbb6 100644
--- a/lib/redmine.rb
+++ b/lib/redmine.rb
@@ -22,6 +22,11 @@ begin
 rescue LoadError
   # RMagick is not available
 end
+begin
+  require 'Redcarpet' unless Object.const_defined?(:Redcarpet)
+rescue LoadError
+  # Redcarpet is not available
+end
 
 require 'redmine/scm/base'
 require 'redmine/access_control'
@@ -267,8 +272,10 @@ end
 
 Redmine::WikiFormatting.map do |format|
   format.register :textile, Redmine::WikiFormatting::Textile::Formatter, Redmine::WikiFormatting::Textile::Helper
-  format.register :markdown, Redmine::WikiFormatting::Markdown::Formatter, Redmine::WikiFormatting::Markdown::Helper,
-    :label => 'Markdown (experimental)'
+  if Object.const_defined?(:Redcarpet)
+    format.register :markdown, Redmine::WikiFormatting::Markdown::Formatter, Redmine::WikiFormatting::Markdown::Helper,
+      :label => 'Markdown (experimental)'
+  end
 end
 
 ActionView::Template.register_template_handler :rsb, Redmine::Views::ApiTemplateHandler
diff --git a/lib/redmine/scm/adapters/abstract_adapter.rb b/lib/redmine/scm/adapters/abstract_adapter.rb
index b6b4e08c3..258b625fb 100644
--- a/lib/redmine/scm/adapters/abstract_adapter.rb
+++ b/lib/redmine/scm/adapters/abstract_adapter.rb
@@ -16,6 +16,7 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 require 'cgi'
+require 'redmine/scm/adapters'
 
 if RUBY_VERSION < '1.9'
   require 'iconv'
diff --git a/test/unit/lib/redmine/wiki_formatting/markdown_formatter.rb b/test/unit/lib/redmine/wiki_formatting/markdown_formatter.rb
index b7409a0bf..191b54ea7 100644
--- a/test/unit/lib/redmine/wiki_formatting/markdown_formatter.rb
+++ b/test/unit/lib/redmine/wiki_formatting/markdown_formatter.rb
@@ -20,6 +20,8 @@ require File.expand_path('../../../../../test_helper', __FILE__)
 class Redmine::WikiFormatting::MarkdownFormatterTest < ActionView::TestCase
   include ApplicationHelper
 
+  if Object.const_defined?(:Redcarpet)
+
   def setup
     @formatter = Redmine::WikiFormatting::Markdown::Formatter
   end
@@ -59,4 +61,6 @@ STR
     text = 'This is a [link](/issues)'
     assert_equal '<p>This is a <a href="/issues">link</a></p>', @formatter.new(text).to_html.strip
   end
+
+  end
 end