diff --git a/ops/nixos/lib/common.nix b/ops/nixos/lib/common.nix
index 7fec64b8c8..71c61a1753 100644
--- a/ops/nixos/lib/common.nix
+++ b/ops/nixos/lib/common.nix
@@ -283,7 +283,8 @@ in
       group = "root";
       reloadOrRestartUnits = [ "nix-daemon.service" ];
     };
-    systemd.services.nix-daemon.serviceConfig.EnvironmentFile = config.my.vault.secrets.nix-daemon.path;
+    # - prefix to make the file existing optional.
+    systemd.services.nix-daemon.serviceConfig.EnvironmentFile = "-${config.my.vault.secrets.nix-daemon.path}";
 
     services.fwupd.enable = true;