diff --git a/frontend/grub-mkrescue-sed.sh b/frontend/grub-mkrescue-sed.sh
index 6abe6edd..f409ca49 100755
--- a/frontend/grub-mkrescue-sed.sh
+++ b/frontend/grub-mkrescue-sed.sh
@@ -26,6 +26,8 @@ echo >&2
 #
 # The mode "mbr_only" implements an alternative layout according to UEFI 2.4,
 # section 2.5.1 and table 16. No GTP, HFS+, or APM.
+# This mode produces a mountable ISO 9660 partition 1 only if variable
+# MKRESCUE_SED_PROTECTIVE is set to "no".
 #
 # The mode "mbr_hfs" is like "mbr_only" but with HFS+ mentioned in APM.
 # It is still compliant to UEFI with no potentially deceiving GPT.
@@ -35,7 +37,8 @@ echo >&2
 # Mode "gpt_appended" represents the same layout as "mbr_only" by GPT rather
 # than by MBR partition table. It differs from "original" by the fact that
 # option -partition_offset 16 is implied and that the first partition may
-# be used to mount the ISO 9660 filesystem.
+# be used to mount the ISO 9660 filesystem. MKRESCUE_SED_PROTECTIVE is ignored,
+# because neat GPT is indicated by the existence of a Protective MBR.
 #
 # These modes avoid duplicate storing of the EFI system partition "efi.img"
 # by xorrisofs option  -e "--interval:appended_partition_${partno}:all::"
@@ -55,10 +58,10 @@ echo >&2
 #  "mjg"         =  ESP in MBR+GPT+APM, with HFS+
 #  "mbr_only"    =  ESP in MBR, without HFS+
 #  "mbr_hfs"     =  ESP in MBR, HFS+ in APM
-#  "gpt_appended" = ESP in GPT
+#  "gpt_appended" = ESP in GPT, without HFS+
 #  $mode"_copy"  =  one of above modes, ESP in ISO and as appended partition
-#  "original"    =  pass arguments unchanged (i.e. no mountable ISO partition)
-mode="mjg"
+#  "original"    =  pass arguments unchanged
+mode="mbr_only"
 if test -n "$MKRESCUE_SED_MODE"
 then
   mode="$MKRESCUE_SED_MODE"