diff --git a/lib/redmine/views/other_formats_builder.rb b/lib/redmine/views/other_formats_builder.rb
index 1f575169..c3c89b24 100644
--- a/lib/redmine/views/other_formats_builder.rb
+++ b/lib/redmine/views/other_formats_builder.rb
@@ -25,7 +25,7 @@ module Redmine
       def link_to(name, options={})
         url = { :format => name.to_s.downcase }.merge(options.delete(:url) || {})
         caption = options.delete(:caption) || name
-        html_options = { :class => name.to_s.downcase }.merge(options)
+        html_options = { :class => name.to_s.downcase, :rel => 'nofollow' }.merge(options)
         @view.content_tag('span', @view.link_to(caption, url, html_options))
       end
     end