diff --git a/iso/builder/build.sh b/iso/builder/build.sh
index fce5b46..90ac606 100755
--- a/iso/builder/build.sh
+++ b/iso/builder/build.sh
@@ -658,6 +658,21 @@ extract_live_grub_entry() {
     return 0
 }
 
+load_live_build_append() {
+    lb_dir="$1"
+    binary_cfg="$lb_dir/config/binary"
+    [ -f "$binary_cfg" ] || return 1
+
+    # config/binary is generated by live-build and contains shell variable
+    # assignments such as LB_BOOTAPPEND_LIVE="boot=live ...".
+    # shellcheck disable=SC1090
+    . "$binary_cfg"
+
+    [ -n "${LB_BOOTAPPEND_LIVE:-}" ] || return 1
+    live_build_append="$LB_BOOTAPPEND_LIVE"
+    return 0
+}
+
 extract_live_isolinux_entry() {
     cfg="$1"
     isolinux_linux="$(awk '/^[[:space:]]*linux[[:space:]]+\/live\// { print; exit }' "$cfg")"
@@ -799,13 +814,18 @@ enforce_live_build_bootloader_assets() {
     grub_dir="$lb_dir/binary/boot/grub"
     isolinux_cfg="$lb_dir/binary/isolinux/live.cfg"
 
+    if ! load_live_build_append "$lb_dir"; then
+        echo "bootloader sync: WARNING: could not load LB_BOOTAPPEND_LIVE from $lb_dir/config/binary" >&2
+        live_build_append=""
+    fi
+
     if [ -f "$grub_cfg" ]; then
         if extract_live_grub_entry "$grub_cfg"; then
             mkdir -p "$grub_dir/live-theme"
             cp "${BUILDER_DIR}/config/bootloaders/grub-efi/config.cfg" "$grub_dir/config.cfg"
             cp "${BUILDER_DIR}/config/bootloaders/grub-efi/theme.cfg" "$grub_dir/theme.cfg"
             cp -R "${BUILDER_DIR}/config/bootloaders/grub-efi/live-theme/." "$grub_dir/live-theme/"
-            write_canonical_grub_cfg "$grub_cfg" "$grub_kernel" "$grub_append" "$grub_initrd"
+            write_canonical_grub_cfg "$grub_cfg" "$grub_kernel" "${live_build_append:-$grub_append}" "$grub_initrd"
             echo "bootloader sync: rewrote binary/boot/grub/grub.cfg with canonical EASY-BEE menu"
         else
             echo "bootloader sync: WARNING: could not extract live entry from $grub_cfg" >&2
@@ -814,7 +834,7 @@ enforce_live_build_bootloader_assets() {
 
     if [ -f "$isolinux_cfg" ]; then
         if extract_live_isolinux_entry "$isolinux_cfg"; then
-            write_canonical_isolinux_cfg "$isolinux_cfg" "$isolinux_kernel" "$isolinux_initrd_path" "$isolinux_append"
+            write_canonical_isolinux_cfg "$isolinux_cfg" "$isolinux_kernel" "$isolinux_initrd_path" "${live_build_append:-$isolinux_append}"
             echo "bootloader sync: rewrote binary/isolinux/live.cfg with canonical EASY-BEE menu"
         else
             echo "bootloader sync: WARNING: could not extract live entry from $isolinux_cfg" >&2