diff --git a/app/models/relative_memo.rb b/app/models/relative_memo.rb
index eeef0eb9..6a470663 100644
--- a/app/models/relative_memo.rb
+++ b/app/models/relative_memo.rb
@@ -17,6 +17,7 @@ class RelativeMemo < ActiveRecord::Base
   # validates_length_of :subject, maximum: 50
   #validates_length_of :content, maximum: 3072
   validate :cannot_reply_to_locked_topic, :on => :create
+  validates_uniqueness_of :osp_id, :scope => [:subject, :context]
 
   acts_as_tree :counter_cache => :replies_count, :order => "#{RelativeMemo.table_name}.created_at ASC"
   acts_as_attachable