diff --git a/nix/modules/knotmirror.nix b/nix/modules/knotmirror.nix
index 461fbe90b..0a85ce419 100644
--- a/nix/modules/knotmirror.nix
+++ b/nix/modules/knotmirror.nix
@@ -117,6 +117,7 @@ in
 
       zoektUrl = mkOption {
         type = types.str;
+        default = "";
         example = "https://zoekt.tngl.boltless.dev/indexserver";
         description = "zoekt-tnglserver url";
       };