diff --git a/app/models/categorization.rb b/app/models/categorization.rb
index 296aa42..b895f86 100644
--- a/app/models/categorization.rb
+++ b/app/models/categorization.rb
@@ -1,12 +1,14 @@
 module Categorization
 
   def add_category_to_object(category, object)
-    connection.execute("insert into #{table_name} (category_id, #{object_id_column}) values(#{category.id}, #{object.id})")
+    if !find(:first, :conditions => {object_id_column => object, :category_id => category} )
+      connection.execute("insert into #{table_name} (category_id, #{object_id_column}) values(#{category.id}, #{object.id})")
 
-    c = category.parent
-    while !c.nil? && !self.find(:first, :conditions => {object_id_column => object, :category_id => c})
-      connection.execute("insert into #{table_name} (category_id, #{object_id_column}, virtual) values(#{c.id}, #{object.id}, 1>0)")
-      c = c.parent
+      c = category.parent
+      while !c.nil? && !self.find(:first, :conditions => {object_id_column => object, :category_id => c})
+        connection.execute("insert into #{table_name} (category_id, #{object_id_column}, virtual) values(#{c.id}, #{object.id}, 1>0)")
+        c = c.parent
+      end
     end
   end
 
diff --git a/test/unit/article_categorization_test.rb b/test/unit/article_categorization_test.rb
index aeec46e..7f3460e 100644
--- a/test/unit/article_categorization_test.rb
+++ b/test/unit/article_categorization_test.rb
@@ -61,4 +61,17 @@ class ArticleCategorizationTest < Test::Unit::TestCase
     end
   end
 
+  should 'not duplicate when adding the parent of a category by witch the article is already categorized' do
+    c1 = Category.create!(:name => 'c1', :environment => Environment.default)
+    c2 = c1.children.create!(:name => 'c2', :environment => Environment.default)
+
+    p = create_user('testuser').person
+    a = p.articles.create!(:name => 'test')
+
+    assert_difference ArticleCategorization, :count, 2 do
+      ArticleCategorization.add_category_to_article(c2, a)
+      ArticleCategorization.add_category_to_article(c1, a)
+    end
+  end
+
 end
--
libgit2 0.21.2