diff --git a/gallery-jquery-fileupload/app/helpers/upload_helper.rb b/gallery-jquery-fileupload/app/helpers/upload_helper.rb
index 574e879..c2602a0 100644
--- a/gallery-jquery-fileupload/app/helpers/upload_helper.rb
+++ b/gallery-jquery-fileupload/app/helpers/upload_helper.rb
@@ -16,7 +16,7 @@ def initialize(options)
         aws_secret_access_key: ENV["AWS_SECRET_ACCESS_KEY"],
         bucket: ENV["AWS_S3_BUCKET"],
         acl: "public-read",
-        expiration: 10.hours.from_now,
+        expiration: 10.hours.from_now.utc.iso8601,
         max_file_size: 500.megabytes,
         as: "file"
       )