diff --git a/lib/modules/nixos/default-module.nix b/lib/modules/nixos/default-module.nix
index 648dc4c..f1fb196 100644
--- a/lib/modules/nixos/default-module.nix
+++ b/lib/modules/nixos/default-module.nix
@@ -89,7 +89,7 @@
     );
     environment.etc = {
       "lytedev/rev".text = config.system.configurationRevision;
-      "lytedev/lastModified".text = self.lastModified or "unknown";
+      "lytedev/lastModified".text = toString (self.lastModified or "unknown");
     };
 
     lyte.shell.enable = lib.mkDefault true;