diff --git a/nixos/modules/services/networking/firefox/sync-server.nix b/nixos/modules/services/networking/firefox/sync-server.nix
index b357eac98b9..58b07e51387 100644
--- a/nixos/modules/services/networking/firefox/sync-server.nix
+++ b/nixos/modules/services/networking/firefox/sync-server.nix
@@ -50,7 +50,8 @@ in
 
       listen.address = mkOption {
         type = types.str;
-        default = "0.0.0.0";
+        default = "127.0.0.1";
+        example = "0.0.0.0";
         description = ''
           Address on which the sync server listen to.
         '';