diff --git a/nixos/modules/services/backup/restic.nix b/nixos/modules/services/backup/restic.nix
index 9b31ff3b582..6ece5a9b5ad 100644
--- a/nixos/modules/services/backup/restic.nix
+++ b/nixos/modules/services/backup/restic.nix
@@ -18,6 +18,7 @@ with lib;
 
         s3CredentialsFile = mkOption {
           type = with types; nullOr str;
+          default = null;
           description = ''
             file containing the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY
             for an S3-hosted repository, in the format of an EnvironmentFile