diff --git a/deploy/nixos/live.nix b/deploy/nixos/live.nix
index 07fe161..00baabc 100644
--- a/deploy/nixos/live.nix
+++ b/deploy/nixos/live.nix
@@ -55,6 +55,12 @@ in
   isoImage = {
     makeEfiBootable = true;
     makeBiosBootable = true;
+    # Apply the isohybrid MBR + GPT/ESP so the image boots when dd'd to a USB
+    # stick — not just from optical media via El Torito. Without this the ISO
+    # has BIOS+UEFI El Torito boot catalogs but no partition table, and picky
+    # firmware (e.g. the Sintra's Aaeon UP Board) won't recognise the USB as
+    # bootable. Requires makeBiosBootable (isohdpfx.bin), set above.
+    makeUsbBootable = true;
     squashfsCompression = "zstd -Xcompression-level 6";
   };