@@ -70,7 +70,7 @@ module Jekyll

       if self.layouts.key? 'category_index'

         dir = self.config['category_dir'] || 'categories'

         self.categories.keys.each do |category|

-          self.write_category_index(File.join(dir, category.gsub(/_|\P{Word}/, '-').gsub(/-{2,}/, '-')), category)

+          self.write_category_index(File.join(dir, category.gsub(/_|\P{Word}/, '-').gsub(/-{2,}/, '-').downcase), category)

         end

       # Throw an exception if the layout couldn't be found.

@@ -107,7 +107,7 @@ module Jekyll

     def category_links(categories)

       dir = @context.registers[:site].config['category_dir']

       categories = categories.sort!.map do |item|

-        "<a class='category' href='/#{dir}/#{item.gsub(/_|\P{Word}/, '-').gsub(/-{2,}/, '-')}/'>#{item}</a>"

+        "<a class='category' href='/#{dir}/#{item.gsub(/_|\P{Word}/, '-').gsub(/-{2,}/, '-').downcase}/'>#{item}</a>"

       end

       case categories.length