diff --git a/lib/nanoc/base/source_data/configuration.rb b/lib/nanoc/base/source_data/configuration.rb
index 595d74fe6b..a3035cb0d6 100644
--- a/lib/nanoc/base/source_data/configuration.rb
+++ b/lib/nanoc/base/source_data/configuration.rb
@@ -20,7 +20,7 @@ class Configuration
     # that lacks some options, the default value will be taken from
     # `DEFAULT_CONFIG`.
     DEFAULT_CONFIG = {
-      text_extensions: %w( css erb haml htm html js less markdown md php rb sass scss txt xhtml xml coffee hb handlebars mustache ms slim rdoc ).sort,
+      text_extensions: %w( atom css erb haml htm html js less markdown md php rb sass scss txt xhtml xml coffee hb handlebars mustache ms slim rdoc ).sort,
       lib_dirs: %w( lib ),
       commands_dirs: %w( commands ),
       output_dir: 'output',