--- 10_linux_zfs	2023-07-28 15:34:32.000000000 +0200
+++ 10_linux_zfs_grub_2.12~rc1	2023-08-01 10:08:36.802829248 +0200
@@ -30,8 +30,6 @@
 export TEXTDOMAIN=grub
 export TEXTDOMAINDIR="${datarootdir}/locale"
 
-set -u
-
 ## Skip early if zfs utils isn't installed (instead of failing on first zpool list)
 if ! `which zfs >/dev/null 2>&1`; then
     exit 0
@@ -420,18 +418,15 @@
     initrd_list=""
     kernel_list=""
     candidate_kernel_list="$(find "${boot_dir}" -maxdepth 1 -type f -regex '.*/\(vmlinuz\|vmlinux\|kernel\)-.*')"
-    while [ -n "${candidate_kernel_list}" ] ; do
-        list_basename="$(echo "${candidate_kernel_list}" | sed -e 's#.*/##')"
-        linux=$(version_find_latest ${list_basename})
-        linux=$(echo "${candidate_kernel_list}" | while read k; do
-            if [ "$(basename "${k}")" = "${linux}" ]; then
-                echo -n "${k}"
-                break
-            fi
-        done)
-        # || true to not abort even if candidate_kernel_list is empty on last entry
-        candidate_kernel_list="$(echo "${candidate_kernel_list}" | fgrep -vx "${linux}"||true)"
 
+    # Perform a reverse version sort on the entire list.
+    # Temporarily replace the '.old' suffix by ' 1' and append ' 2' for all
+    # other files to order the '.old' files after their non-old counterpart
+    # in reverse-sorted order.
+
+    reverse_sorted_list=$(echo $candidate_kernel_list | tr ' ' '\n' | sed -e 's/\.old$/ 1/; / 1$/! s/$/ 2/' | version_sort -r | sed -e 's/ 1$/.old/; s/ 2$//')
+
+    for linux in ${reverse_sorted_list}; do
         if ! grub_file_is_not_garbage "${linux}" ; then
             continue
         fi