diff --git a/app/models/topic_embed.rb b/app/models/topic_embed.rb
index 1e9f06a3223..502409d3c19 100644
--- a/app/models/topic_embed.rb
+++ b/app/models/topic_embed.rb
@@ -34,7 +34,7 @@ class TopicEmbed < ActiveRecord::Base
       contents = first_paragraph_from(contents)
     end
     contents ||= ''
-    contents = +contents << imported_from_html(url)
+    contents = contents.dup << imported_from_html(url)
 
     url = normalize_url(url)