diff --git a/doc/index.md b/doc/index.md
index 307f827..25fa487 100644
--- a/doc/index.md
+++ b/doc/index.md
@@ -28,6 +28,9 @@ To launch optional scripts after 'upgrade', you can create any hook regarding:
 2. script should be named with prefix 'after-upgrade', example: `after-upgrade-1.bash`
 3. script should be executable, ie: `chmod +x after-upgrade-1.bash`
 
+Be aware: no matter a failure happens during processing a hook, it will get bypassed!
+As so the whole process of upgrading keeps running on.
+
 Rk: hooks.d/ respects natural order,
 ie: `after-upgrade-0.bash` will perform before `after-upgrade-1.bash`