diff --git a/configuration.nix b/configuration.nix
index 1727523..c4dc575 100644
--- a/configuration.nix
+++ b/configuration.nix
@@ -230,15 +230,21 @@
         ROOT_SRC="$($FINDMNT -n -o SOURCE / || true)"
         [ -z "$ROOT_SRC" ] && exit 0
 
-        DEV="$ROOT_SRC"
-        while PARENT="$($LSBLK -no PKNAME "$DEV" 2>/dev/null)"; [ -n "$PARENT" ]; do
-          DEV="/dev/$PARENT"
-        done
+        # Resolve to top-level disk exactly once
+        PARENT="$($LSBLK -ndo PKNAME "$ROOT_SRC" 2>/dev/null || true)"
+        if [ -n "$PARENT" ]; then
+          ROOT_DEV="/dev/$PARENT"
+        else
+          ROOT_DEV="$ROOT_SRC"
+        fi
 
-        DEV_NAME="$($BASENAME "$DEV")"
+        DEV_NAME="$($BASENAME "$ROOT_DEV")"
+
+        # Sanity check: ensure device exists before watching
+        [ ! -e "/sys/class/block/$DEV_NAME" ] && exit 0
 
         while [ -e "/sys/class/block/$DEV_NAME" ]; do
-          $SLEEP 0.5
+          $SLEEP 1
         done
 
         $SYSTEMCTL poweroff