diff --git a/hosts/common/core/impermanence.nix b/hosts/common/core/impermanence.nix
index fe82a00..7cdc0f2 100644
--- a/hosts/common/core/impermanence.nix
+++ b/hosts/common/core/impermanence.nix
@@ -22,6 +22,7 @@
     ];
     directories = [
       "/var/log"
+      "/var/lib/nixos"
     ];
   };
 }
diff --git a/modules/microvms.nix b/modules/microvms.nix
index 12d87ec..158f89a 100644
--- a/modules/microvms.nix
+++ b/modules/microvms.nix
@@ -72,6 +72,15 @@
         ];
       };
 
+      # Add a writable store overlay, but since this is always ephemeral
+      # disable any store optimization from nix.
+      microvm.writableStoreOverlay = "/nix/.rw-store";
+      nix = {
+        settings.auto-optimise-store = mkForce false;
+        optimise.automatic = mkForce false;
+        gc.automatic = mkForce false;
+      };
+
       extra.networking.renameInterfacesByMac.${vmCfg.linkName} = vmCfg.mac;
 
       systemd.network.networks = {