diff --git a/installer/default.nix b/installer/default.nix
index 1639f42..ae11a1f 100644
--- a/installer/default.nix
+++ b/installer/default.nix
@@ -204,10 +204,13 @@ in {
     "${modulesPath}/installer/cd-dvd/installation-cd-minimal.nix"
   ];
 
-  # Ventoy's initrd does not support zstd (the NixOS 25.11 default), which
-  # causes a -110 timeout and "unable to read id index table" on boot.
-  # xz is universally supported by Ventoy across all versions.
-  isoImage.squashfsCompression = "xz -Xdict-size 100%";
+  # Ventoy presents the ISO as a virtual CDROM without the filesystem label
+  # that NixOS stage-1 expects (nixos-minimal-*). Stage-1 cannot find the
+  # loop device for nix-store.squashfs, causing "unable to read id index table".
+  # copytoram loads the entire ISO into RAM before the squashfs mount, removing
+  # the dependency on the Ventoy device remaining accessible during boot.
+  # See: https://github.com/NixOS/nixpkgs/issues/245101
+  boot.kernelParams = [ "copytoram" ];
 
   services.getty.autologinUser = lib.mkForce "root";