diff --git a/lib/noosfero/vote_ext.rb b/lib/noosfero/vote_ext.rb
index 12f78f6..be349ca 100644
--- a/lib/noosfero/vote_ext.rb
+++ b/lib/noosfero/vote_ext.rb
@@ -2,6 +2,10 @@ require_dependency 'models/vote'
 
 class Vote
 
-  validates_uniqueness_of :voteable_id, :scope => [:voteable_type, :voter_type, :voter_id]
+  validates_uniqueness_of :voteable_id, :scope => [:voteable_type, :voter_type, :voter_id], :if => :allow_duplicated_vote?
+
+  def allow_duplicated_vote?
+    voter.present?
+  end
 
 end
--
libgit2 0.21.2