diff --git a/wfvm/autounattend.nix b/wfvm/autounattend.nix
index 065c8fd..1421850 100644
--- a/wfvm/autounattend.nix
+++ b/wfvm/autounattend.nix
@@ -14,7 +14,6 @@
 , services ? {}
 , impureShellCommands ? []
 , driveLetter ? "D:"
-, efi ? true
 , imageSelection ? "Windows 11 Pro N"
 , ...
 }:
@@ -121,8 +120,7 @@ let
   # Windows expects a flat list of users while we want to manage them as a set
   flatUsers = builtins.attrValues (builtins.mapAttrs (name: s: s // { inherit name; }) users);
 
-  diskId =
-    if efi then 2 else 1;
+  diskId = 2;
 
   autounattendXML = pkgs.writeText "autounattend.xml" ''
     <?xml version="1.0" encoding="utf-8"?>
@@ -172,12 +170,12 @@ let
               <CreatePartitions>
                 <CreatePartition wcm:action="add">
                   <Order>1</Order>
-                  <Type>${if efi then "EFI" else "Primary"}</Type>
+                  <Type>EFI</Type>
                   <Size>300</Size>
                 </CreatePartition>
                 <CreatePartition wcm:action="add">
                   <Order>2</Order>
-                  <Type>${if efi then "MSR" else "Primary"}</Type>
+                  <Type>MSR</Type>
                   <Size>16</Size>
                 </CreatePartition>
                 <CreatePartition wcm:action="add">
@@ -189,7 +187,7 @@ let
               <ModifyPartitions>
                 <ModifyPartition wcm:action="add">
                   <Order>1</Order>
-                  <Format>${if efi then "FAT32" else "NTFS"}</Format>
+                  <Format>FAT32</Format>
                   <Label>System</Label>
                   <PartitionID>1</PartitionID>
                 </ModifyPartition>
diff --git a/wfvm/utils.nix b/wfvm/utils.nix
index fa5ea78..f4fe9b2 100644
--- a/wfvm/utils.nix
+++ b/wfvm/utils.nix
@@ -1,4 +1,4 @@
-{ pkgs, baseRtc ? "2022-10-10T10:10:10", cores ? "4", qemuMem ? "4G", efi ? true }:
+{ pkgs, baseRtc ? "2022-10-10T10:10:10", cores ? "4", qemuMem ? "4G" }:
 
 rec {
   # qemu_test is a smaller closure only building for a single system arch
@@ -18,7 +18,6 @@ rec {
     "-rtc base=${baseRtc}"
     "-device qemu-xhci"
     "-device virtio-net-pci,netdev=n1"
-  ] ++ pkgs.lib.optionals efi [
     "-bios ${OVMF.fd}/FV/OVMF.fd"
   ] ++ extraFlags;
 
diff --git a/wfvm/win.nix b/wfvm/win.nix
index 081b36b..58ca88e 100644
--- a/wfvm/win.nix
+++ b/wfvm/win.nix
@@ -7,13 +7,12 @@
 , users ? {}
 # autounattend always installs index 1, so this default is backward-compatible
 , imageSelection ? "Windows 11 Pro N"
-, efi ? true
 , ...
 }@attrs:
 
 let
   lib = pkgs.lib;
-  utils = import ./utils.nix { inherit pkgs efi; };
+  utils = import ./utils.nix { inherit pkgs; };
   inherit (pkgs) guestfs-tools;
 
   # p7zip on >20.03 has known vulns but we have no better option
@@ -95,7 +94,7 @@ let
         "usb-storage,drive=virtio-win"
         # USB boot
         "-drive"
-        "id=win-install,file=${if efi then "usb" else "cd"}image.img,if=none,format=raw,readonly=on,media=${if efi then "disk" else "cdrom"}"
+        "id=win-install,file=usbimage.img,if=none,format=raw,readonly=on,media=disk"
         "-device"
         "usb-storage,drive=win-install"
         # Output image
@@ -124,11 +123,7 @@ let
 
         cp ${autounattend.autounattendXML} win/autounattend.xml
 
-        ${if efi then ''
         virt-make-fs --partition --type=fat win/ usbimage.img
-        '' else ''
-        ${pkgs.cdrkit}/bin/mkisofs -iso-level 4 -l -R -udf -D -b boot/etfsboot.com -no-emul-boot -boot-load-size 8 -hide boot.catalog -eltorito-alt-boot -o cdimage.img win/
-        ''}
         rm -rf win
 
         # Qemu requires files to be rw