diff --git a/README.md b/README.md
index 5ed529d..771fe12 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,8 @@ NOTE: if ``test_ddl_triggers`` fails it's likely due to an incomplete
 
 NOTE: you need to run the installcheck as a superuser, use PGUSER
       env variable if needed, like: PGUSER=postgres make installcheck
+      
+NOTE: the tests need to run against a **clean postgres instance**, if you have some roles already created test will likely fail due `publicuser` not being dropped.
 
 Enable database
 ---------------