diff --git a/backup.nix b/backup.nix
index c7e3b64..f29dea3 100644
--- a/backup.nix
+++ b/backup.nix
@@ -46,7 +46,7 @@ in
   };
   config = lib.mkIf cfg.enable {
     systemd.services."backup-helper@" = {
-      after = "network-online.target";
+      after = [ "network-online.target" ];
       environment = {
         RESTIC_REPOSITORY = cfg.restic-repository;
       } // lib.attrsets.optionalAttrs (builtins.hasAttr "password-file" cfg) {