diff --git a/lib/postal/message_db/delivery.rb b/lib/postal/message_db/delivery.rb
index e5d0e8c..f06c76b 100644
--- a/lib/postal/message_db/delivery.rb
+++ b/lib/postal/message_db/delivery.rb
@@ -48,7 +48,7 @@ module Postal
           message: @message.webhook_hash,
           status: status,
           details: details,
-          output: output.to_s.force_encoding("UTF-8").scrub.truncate(512),
+          output: output.to_s.dup.force_encoding("UTF-8").scrub.truncate(512),
           sent_with_ssl: sent_with_ssl,
           timestamp: @attributes["timestamp"],
           time: time