diff --git a/lib/gollum/markup.rb b/lib/gollum/markup.rb
index fe35c476..7602b7fd 100644
--- a/lib/gollum/markup.rb
+++ b/lib/gollum/markup.rb
@@ -488,8 +488,10 @@ module Gollum
         # extract lang from { .ruby } or { #stuff .ruby .indent }
         # see http://johnmacfarlane.net/pandoc/README.html#delimited-code-blocks
 
-        lang = lang.match(/\.([^}\s]+)/)
-        lang = lang[1] unless lang.nil?
+        if lang
+            lang = lang.match(/\.([^}\s]+)/)
+            lang = lang[1] unless lang.nil?
+        end
 
         @codemap[id] = cached   ?
           { :output => cached } :
diff --git a/test/test_markup.rb b/test/test_markup.rb
index 056028ff..13b05708 100644
--- a/test/test_markup.rb
+++ b/test/test_markup.rb
@@ -212,6 +212,19 @@ context "Markup" do
     assert_equal expected, output
   end
 
+  # Issue #568
+  test "tilde code blocks without a language" do
+    page = 'test_rgx'
+    @wiki.write_page(page, :markdown,
+      %Q(~~~
+'hi'
+~~~
+      ), commit_details)
+    output = @wiki.page(page).formatted_data
+    expected = %Q{<div class=\"highlight\"><pre><span class=\"s\">'hi'</span>\n</pre></div>}
+    assert_equal expected, output
+  end
+
   test "tilda code blocks #537" do
     page = 'test_rgx'
     @wiki.write_page(page, :markdown,