diff --git a/lib/mws-rb/api/feeds.rb b/lib/mws-rb/api/feeds.rb
index <HASH>..<HASH> 100644
--- a/lib/mws-rb/api/feeds.rb
+++ b/lib/mws-rb/api/feeds.rb
@@ -18,7 +18,7 @@ module MWS
         params = params.except(:merchant_id, :message_type, :message, :messages, :skip_schema_validation)
         call(:submit_feed, params.merge!(
           request_params: {
-            format: "xml",
+            format: :xml,
             headers: {
               "Content-MD5" => xml_envelope.md5
             },
Fix format option used in the submit_feed method