diff --git a/app/models/category.rb b/app/models/category.rb
index 4f860ce..c6691c2 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -1,6 +1,7 @@
 class Category < ActiveRecord::Base
 
   validates_presence_of :name, :environment_id
+  validates_uniqueness_of :slug,:scope => [ :environment_id, :parent_id ], :message => N_('%{fn} is already being used by another category.')
   belongs_to :environment
 
   acts_as_tree :order => 'name'
diff --git a/test/unit/category_test.rb b/test/unit/category_test.rb
index 1cb9503..e2a8c02 100644
--- a/test/unit/category_test.rb
+++ b/test/unit/category_test.rb
@@ -118,7 +118,7 @@ class CategoryTest < Test::Unit::TestCase
     assert_equal 'parent/child', c2.path
   end
 
-  def test_save_
+  def test_should_set_path_correctly_before_saving
     c1 = Category.create!(:name => 'parent', :environment_id => @env.id)
 
     c2 = Category.new(:name => 'child', :environment_id => @env.id)
@@ -128,4 +128,13 @@ class CategoryTest < Test::Unit::TestCase
     assert_equal 'parent/child', c2.path
   end
 
+  def test_should_refuse_to_duplicate_slug_under_the_same_parent
+    c1 = Category.create!(:name => 'test category', :environment_id => @env.id)
+    c2 = Category.new(:name => 'Test: Category', :environment_id => @env.id)
+
+    assert !c2.valid?
+    assert c2.errors.invalid?(:slug)
+
+  end
+
 end
--
libgit2 0.21.2