diff --git a/lib/noosfero.rb b/lib/noosfero.rb
index d7ec786..a618fa4 100644
--- a/lib/noosfero.rb
+++ b/lib/noosfero.rb
@@ -54,7 +54,7 @@ module Noosfero
   end
 
   def self.identifier_format
-    '[a-z0-9][a-z0-9~.]*([_\-][a-z0-9~.]+)*'
+    '(?!index)[a-z0-9][a-z0-9~.]*([_\-][a-z0-9~.]+)*'
   end
 
   def self.default_hostname
--
libgit2 0.21.2