diff --git a/app/views/list/list.rss.erb b/app/views/list/list.rss.erb
index 78193a8f0d7..d0f6c14957c 100644
--- a/app/views/list/list.rss.erb
+++ b/app/views/list/list.rss.erb
@@ -6,7 +6,7 @@
     <title><%= @title %></title>
     <link><%= @link %></link>
     <description><%= @description %></description>
-    <% if lang %><language><%= lang%></language><% end %>
+    <% if lang %><language><%= lang.sub('_', '-')%></language><% end %>
     <% if @topic_list.topics && @topic_list.topics.length > 0 %>
       <lastBuildDate><%= @topic_list.topics.first.created_at.rfc2822 %></lastBuildDate>
       <atom:link href="<%= @atom_link %>" rel="self" type="application/rss+xml" />
diff --git a/app/views/topics/show.rss.erb b/app/views/topics/show.rss.erb
index aa7d08c4a85..a7efff93641 100644
--- a/app/views/topics/show.rss.erb
+++ b/app/views/topics/show.rss.erb
@@ -7,7 +7,7 @@
     <title><%= @topic_view.title %></title>
     <link><%= topic_url %></link>
     <description><%= @topic_view.posts.first.raw %></description>
-    <%= "<language>#{lang}</language>" if lang %>
+    <% if lang %><language><%= lang.sub('_', '-')%></language><% end %>
     <lastBuildDate><%= @topic_view.topic.bumped_at.rfc2822 %></lastBuildDate>
     <category><%= @topic_view.topic.category.name %></category>
     <atom:link href="<%= topic_url %>.rss" rel="self" type="application/rss+xml" />