diff --git a/app/models/repository.rb b/app/models/repository.rb
index 475445a..83c5b7c 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -38,7 +38,7 @@ class Repository < ActiveRecord::Base
 
   validates_length_of :password, :maximum => 255, :allow_nil => true
   validates_length_of :identifier, :maximum => IDENTIFIER_MAX_LENGTH, :allow_blank => true
-  validates_uniqueness_of :identifier, :scope => :project_id, :allow_blank => true
+  validates_uniqueness_of :identifier, :scope => :project_id
   validates_exclusion_of :identifier, :in => %w(browse show entry raw changes annotate diff statistics graph revisions revision)
   # donwcase letters, digits, dashes, underscores but not digits only
   validates_format_of :identifier, :with => /\A(?!\d+$)[a-z0-9\-_]*\z/, :allow_blank => true
diff --git a/test/unit/repository_test.rb b/test/unit/repository_test.rb
index debac51..8f8cb9a 100644
--- a/test/unit/repository_test.rb
+++ b/test/unit/repository_test.rb
@@ -76,6 +76,24 @@ class RepositoryTest < ActiveSupport::TestCase
     assert_equal repository, project.repository
   end
 
+  def test_2_repositories_with_same_identifier_in_different_projects_should_be_valid
+    Repository::Subversion.create!(:project_id => 2, :identifier => 'foo', :url => 'file:///foo')
+    r = Repository::Subversion.new(:project_id => 3, :identifier => 'foo', :url => 'file:///bar')
+    assert r.save
+  end
+
+  def test_2_repositories_with_same_identifier_should_not_be_valid
+    Repository::Subversion.create!(:project_id => 3, :identifier => 'foo', :url => 'file:///foo')
+    r = Repository::Subversion.new(:project_id => 3, :identifier => 'foo', :url => 'file:///bar')
+    assert !r.save
+  end
+
+  def test_2_repositories_with_blank_identifier_should_not_be_valid
+    Repository::Subversion.create!(:project_id => 3, :identifier => '', :url => 'file:///foo')
+    r = Repository::Subversion.new(:project_id => 3, :identifier => '', :url => 'file:///bar')
+    assert !r.save
+  end
+
   def test_first_repository_should_be_set_as_default
     repository1 = Repository::Subversion.new(
                       :project => Project.find(3),