diff --git a/lib/jekyll/converters/markdown.rb b/lib/jekyll/converters/markdown.rb
index baeb9bf7..485cac82 100644
--- a/lib/jekyll/converters/markdown.rb
+++ b/lib/jekyll/converters/markdown.rb
@@ -26,7 +26,7 @@ module Jekyll
       end
 
       def matches(ext)
-        rgx = '(' + @config['markdown_ext'].gsub(',','|') +')'
+        rgx = '^\.(' + @config['markdown_ext'].gsub(',','|') +')$'
         ext =~ Regexp.new(rgx, Regexp::IGNORECASE)
       end
 
diff --git a/test/source/_posts/2013-08-01-mkdn-extension.mkdn b/test/source/_posts/2013-08-01-mkdn-extension.mkdn
new file mode 100644
index 00000000..e69de29b
diff --git a/test/test_generated_site.rb b/test/test_generated_site.rb
index dd24187f..801675bf 100644
--- a/test/test_generated_site.rb
+++ b/test/test_generated_site.rb
@@ -14,7 +14,7 @@ class TestGeneratedSite < Test::Unit::TestCase
     end
 
     should "ensure post count is as expected" do
-      assert_equal 35, @site.posts.size
+      assert_equal 36, @site.posts.size
     end
 
     should "insert site.posts into the index" do
diff --git a/test/test_post.rb b/test/test_post.rb
index e38af0fa..57979c65 100644
--- a/test/test_post.rb
+++ b/test/test_post.rb
@@ -562,6 +562,13 @@ class TestPost < Test::Unit::TestCase
       assert conv.kind_of? Jekyll::Converters::Markdown
     end
 
+    should "process .mkdn under text if it is not in the markdown config" do
+      @site.config['markdown_ext'] = 'markdown,mkd,md,text'
+      post = setup_post '2013-08-01-mkdn-extension.mkdn'
+      conv = post.converter
+      assert conv.kind_of? Jekyll::Converters::Identity
+    end
+
     should "process .text as textile under alternate configuration" do
       @site.config['textile_ext'] = 'textile,text'
       post = setup_post '2011-04-12-text-extension.text'