diff --git a/actionpack/lib/action_controller/mime_type.rb b/actionpack/lib/action_controller/mime_type.rb
index 6a33fdc19a28a6b6e16d86772202d8f20362bf96..13b00c5984a508997bd9084b45c64a1b7c89427b 100644
--- a/actionpack/lib/action_controller/mime_type.rb
+++ b/actionpack/lib/action_controller/mime_type.rb
@@ -30,27 +30,30 @@ def ==(mime_type)
     end
   end
 
-  ALL  = Type.new "*/*", :all
-  HTML = Type.new "text/html", :html
-  JS   = Type.new "text/javascript", :js, %w( application/javascript application/x-javascript )
-  XML  = Type.new "text/xml", :xml, %w( application/xml application/x-xml )
-  RSS  = Type.new "application/rss+xml", :rss
-  ATOM = Type.new "application/atom+xml", :atom
-  YAML = Type.new "application/x-yaml", :yaml
+  ALL   = Type.new "*/*", :all
+  HTML  = Type.new "text/html", :html, %w( application/xhtml+xml )
+  JS    = Type.new "text/javascript", :js, %w( application/javascript application/x-javascript )
+  XML   = Type.new "application/xml", :xml, %w( text/xml application/x-xml )
+  RSS   = Type.new "application/rss+xml", :rss
+  ATOM  = Type.new "application/atom+xml", :atom
+  YAML  = Type.new "application/x-yaml", :yaml
 
   LOOKUP = Hash.new { |h, k| h[k] = Type.new(k) }
 
   LOOKUP["*/*"]                      = ALL
+
   LOOKUP["text/html"]                = HTML
-  LOOKUP["application/rss+xml"]      = RSS
-  LOOKUP["application/atom+xml"]     = ATOM
-  LOOKUP["application/x-yaml"]       = YAML
+  LOOKUP["application/xhtml+xml"]    = HTML
+
+  LOOKUP["application/xml"]          = XML
+  LOOKUP["text/xml"]                 = XML
+  LOOKUP["application/x-xml"]        = XML
 
   LOOKUP["text/javascript"]          = JS
   LOOKUP["application/javascript"]   = JS
   LOOKUP["application/x-javascript"] = JS
 
-  LOOKUP["text/xml"]                 = XML
-  LOOKUP["application/xml"]          = XML
-  LOOKUP["application/x-xml"]        = XML
+  LOOKUP["application/rss+xml"]      = RSS
+  LOOKUP["application/atom+xml"]     = ATOM
+  LOOKUP["application/x-yaml"]       = YAML
 end
\ No newline at end of file
diff --git a/actionpack/test/controller/mime_responds_test.rb b/actionpack/test/controller/mime_responds_test.rb
index 159d57f1c399e72fe744117ba3e813438d40a65d..6fcaaf302d8a3de69eb337b4c1256f950b247622 100644
--- a/actionpack/test/controller/mime_responds_test.rb
+++ b/actionpack/test/controller/mime_responds_test.rb
@@ -183,4 +183,16 @@ def test_custom_types
     get :custom_type_handling
     assert_equal 'HTML', @response.body
   end
+
+  def test_xhtml_alias
+    @request.env["HTTP_ACCEPT"] = "application/xhtml+xml,application/xml"
+    get :html_or_xml
+    assert_equal 'HTML', @response.body
+  end
+  
+  def test_firefox_simulation
+    @request.env["HTTP_ACCEPT"] = "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
+    get :html_or_xml
+    assert_equal 'HTML', @response.body
+  end
 end
\ No newline at end of file