diff --git a/nixos/modules/virtualisation/openstack-config.nix b/nixos/modules/virtualisation/openstack-config.nix
index d5e862da0ea4..c2da5d0d2301 100644
--- a/nixos/modules/virtualisation/openstack-config.nix
+++ b/nixos/modules/virtualisation/openstack-config.nix
@@ -20,6 +20,7 @@ in
   config = {
     fileSystems."/" = {
       device = "/dev/disk/by-label/nixos";
+      fsType = "ext4";
       autoResize = true;
     };