diff --git a/contrib/README.md b/contrib/README.md
index ab20f71..f8ca0b9 100644
--- a/contrib/README.md
+++ b/contrib/README.md
@@ -140,7 +140,7 @@ rm ~/Library/LaunchAgents/se.jordbo.mempalace-session.plist
 
 **Why:** simpler, ubiquitous, works on any UNIX. No `loginctl enable-linger` dance, no user-units awareness required.
 
-**Caveats:** no "persistent" semantics (a missed run while the machine was off stays missed); default cron output goes to mail or is silently dropped if no MTA.
+**Caveats:** no "persistent" semantics (a missed run while the machine was off stays missed); default cron output goes to mail or is silently dropped if no MTA. Also: **cron is not installed by default on minimal Debian/Ubuntu hosts** (nor on most container images). Check with `command -v crontab` — if absent, `sudo apt install cron` (or equivalent) first, or use the systemd timer instead.
 
 **Install:**