diff --git a/debi.sh b/debi.sh
index 8c288b4..96eec5c 100755
--- a/debi.sh
+++ b/debi.sh
@@ -436,7 +436,12 @@ if [ "$disk_partitioning" = true ]; then
 
 d-i partman-auto/method string regular
 EOF
-    [ -n "$disk" ] && echo "d-i partman-auto/disk string $disk" | $save_preseed
+    if [ -n "$disk" ]; then
+        echo "d-i partman-auto/disk string $disk" | $save_preseed
+    else
+        # shellcheck disable=SC2016
+        echo 'd-i partman/early_command string debconf-set partman-auto/disk "$(list-devices disk | head -n1 )"'
+    fi
 
     [ "$force_gpt" = true ] && echo 'd-i partman-partitioning/default_label string gpt' | $save_preseed