diff --git a/nix/modules/default/gw-sharding.nix b/nix/modules/default/gw-sharding.nix
index 5b83e99..9358aca 100644
--- a/nix/modules/default/gw-sharding.nix
+++ b/nix/modules/default/gw-sharding.nix
@@ -18,6 +18,7 @@
     extraGatewayPorts = lib.mkOption {
       type = lib.types.listOf lib.types.port;
       description = "Extra gateway ports";
+      default = [];
     };
   };