diff --git a/rswag-specs/lib/rswag/specs/swagger_formatter.rb b/rswag-specs/lib/rswag/specs/swagger_formatter.rb
index d16aeb2..7a8687a 100644
--- a/rswag-specs/lib/rswag/specs/swagger_formatter.rb
+++ b/rswag-specs/lib/rswag/specs/swagger_formatter.rb
@@ -48,14 +48,17 @@ module Rswag
 
       def pretty_generate(doc)
         if @config.swagger_format == :yaml
-          # NOTE: Yaml will quite happily embed ruby-only classes such as symbols.
-          # clean_doc = stringify(doc)
-          YAML.dump(doc)
+          YAML.dump(doc.deep_stringify_keys)
         else # config errors are thrown in 'def swagger_format', no throw needed here
           JSON.pretty_generate(doc)
         end
       end
 
+      def deep_stringify_hash_keys(doc)
+
+        doc
+      end
+
       def metadata_to_swagger(metadata)
         response_code = metadata[:response][:code]
         response = metadata[:response].reject { |k,v| k == :code }