diff --git a/modules/cluster/deployment-options.nix b/modules/cluster/deployment-options.nix
index 31aa761c..4f77f516 100644
--- a/modules/cluster/deployment-options.nix
+++ b/modules/cluster/deployment-options.nix
@@ -44,9 +44,10 @@
   config = {
     # HACK: Avoid conflicts when building a NixOS configuration on Hydra
     boot.loader.grub.enable = false;
-    fileSystems."/" = {
+    fileSystems."/" = lib.mkDefault {
       device = "rootfs";
       fsType = "tmpfs";
+      options = [ "size=50%,mode=0755" ];
     };
   };
 }