diff --git a/app/models/user.rb b/app/models/user.rb
index 737a8cc8e..906420ed4 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -38,7 +38,8 @@ class User < ActiveRecord::Base
   attr_protected :login, :admin, :password, :password_confirmation, :hashed_password
 	
   validates_presence_of :login, :firstname, :lastname, :mail, :if => Proc.new { |user| !user.is_a?(AnonymousUser) }
-  validates_uniqueness_of :login, :mail	
+  validates_uniqueness_of :login, :if => Proc.new { |user| !user.login.blank? }
+  validates_uniqueness_of :mail, :if => Proc.new { |user| !user.mail.blank? }
   # Login must contain lettres, numbers, underscores only
   validates_format_of :login, :with => /^[a-z0-9_\-@\.]*$/i
   validates_length_of :login, :maximum => 30