diff --git a/app/models/post.rb b/app/models/post.rb
index f31c33b6..36a0b02e 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -267,7 +267,7 @@ class Post
     # Y que no se procese liquid
     yaml['liquid'] = false
     yaml['usuaries'] = usuaries.map(&:id).uniq
-    yaml['created_at'] ||= modified_at
+    yaml['created_at'] ||= modified_at.dup
     yaml['last_modified_at'] = modified_at
 
     "#{yaml.to_yaml}---\n\n#{body}"