diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index 6e0dc065387..7dfbc38efee 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -110,6 +110,7 @@ let
 
   # Generate a hard disk image containing a /boot partition and GRUB
   # in the MBR.  Used when the `useBootLoader' option is set.
+  # FIXME: use nixos/lib/make-disk-image.nix.
   bootDisk =
     pkgs.vmTools.runInLinuxVM (
       pkgs.runCommand "nixos-boot-disk"