diff --git a/autoinstall/build-iso.sh b/autoinstall/build-iso.sh
index 2887759..5d048d5 100644
--- a/autoinstall/build-iso.sh
+++ b/autoinstall/build-iso.sh
@@ -68,10 +68,28 @@ sed -i "s/set timeout_style=.*/set timeout_style=countdown/" "$GRUB_CFG"
 sed -i "/^\s*linux.*vmlinuz/s/$/ autoinstall quiet ds=nocloud;s=\/cdrom\/nocloud\//" "$GRUB_CFG"
 echo "✓ GRUB patched"
 
-# ── Get MBR template from original ISO ─────────
+# ── Extract MBR and EFI partition from original ISO ────
+echo "→ Extracting boot data from original ISO..."
 MBR_TEMPLATE=$(mktemp)
+EFI_IMG=$(mktemp)
 dd if="$ORIGINAL_ISO" bs=1 count=432 of="$MBR_TEMPLATE" 2>/dev/null
 
+# Find EFI partition (partition 2) start and size in 512-byte sectors
+EFI_LINE=$(fdisk -l "$ORIGINAL_ISO" 2>/dev/null | grep "EFI")
+echo "  EFI partition info: $EFI_LINE"
+EFI_START=$(echo "$EFI_LINE" | awk '{print $2}')
+EFI_SIZE=$(echo  "$EFI_LINE" | awk '{print $4}')
+
+if [ -z "$EFI_START" ] || [ -z "$EFI_SIZE" ]; then
+  echo "ERROR: Could not detect EFI partition in ISO."
+  echo "Run: fdisk -l $ORIGINAL_ISO"
+  exit 1
+fi
+
+dd if="$ORIGINAL_ISO" bs=512 skip="$EFI_START" count="$EFI_SIZE" \
+   of="$EFI_IMG" 2>/dev/null
+echo "✓ EFI partition extracted (start=$EFI_START, size=$EFI_SIZE)"
+
 # ── Repack ISO ─────────────────────────────────
 echo "→ Repacking ISO (this takes ~2 minutes)..."
 xorriso -as mkisofs \
@@ -81,8 +99,7 @@ xorriso -as mkisofs \
   --grub2-mbr "$MBR_TEMPLATE" \
   -partition_offset 16 \
   --mbr-force-bootable \
-  -append_partition 2 28732ac11ff8d211ba4b00a0c93ec93b \
-    "$WORK_DIR/boot/grub/efi.img" \
+  -append_partition 2 28732ac11ff8d211ba4b00a0c93ec93b "$EFI_IMG" \
   -appended_part_as_gpt \
   -iso_mbr_part_type a2a0d0ebe5b9334487c068b6b72699c7 \
   -c "/boot.catalog" \