diff --git a/install_on_debian.md b/install_on_debian.md
index c1efaf14..1d6e82e6 100644
--- a/install_on_debian.md
+++ b/install_on_debian.md
@@ -8,7 +8,7 @@
 
 An ARM box, a VPS, a dedicated server, a standard x86 computer, an old Macintosh, ...
 
-* with **Debian 9** (Stretch) installed
+* with **Debian 9** (Stretch) installed <small>(with kernel >= 3.12)</small>
 * connected to the Internet
 * with a direct **root access** or via SSH