diff --git a/middleman-core/lib/middleman-core/extensions/directory_indexes.rb b/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
index e58682db..cef88868 100644
--- a/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
+++ b/middleman-core/lib/middleman-core/extensions/directory_indexes.rb
@@ -11,7 +11,7 @@ class Middleman::Extensions::DirectoryIndexes < ::Middleman::Extension
     index_file = app.config[:index_file]
     new_index_path = "/#{index_file}"
 
-    extensions = %w(.htm .html .php)
+    extensions = %w(.htm .html .php .xhtml)
 
     resources.each do |resource|
       # Check if it would be pointless to reroute