diff --git a/module/Zapret.nix b/module/Zapret.nix
index 9228707..1c9f952 100644
--- a/module/Zapret.nix
+++ b/module/Zapret.nix
@@ -7,26 +7,22 @@
 let
   cfg = config.module.zapret;
 
-  whitelist =
-    if cfg.whitelist != null then
-      "--hostlist ${pkgs.writeText "zapret-whitelist" (lib.concatStringsSep "\n" cfg.whitelist)}"
-    else
-      "";
+  whitelist = lib.optionalString (
+    cfg.whitelist != null
+  ) "--hostlist ${pkgs.writeText "zapret-whitelist" (lib.concatStringsSep "\n" cfg.whitelist)}";
 
   blacklist =
-    if cfg.blacklist != null then
-      "--hostlist-exclude ${pkgs.writeText "zapret-blacklist" (lib.concatStringsSep "\n" cfg.blacklist)}"
-    else
-      "";
+    lib.optionalString (cfg.blacklist != null)
+      "--hostlist-exclude ${pkgs.writeText "zapret-blacklist" (lib.concatStringsSep "\n" cfg.blacklist)}";
 
   ports = if cfg.httpSupport then "80,443" else "443";
 in
 {
   options.module.zapret = {
-    enable = lib.mkEnableOption "Enable Zapret DPI bypass service.";
+    enable = lib.mkEnableOption "the Zapret DPI bypass service.";
     package = lib.mkPackageOption pkgs "zapret" { };
     params = lib.mkOption {
-      default = null;
+      default = [ ];
       type = with lib.types; listOf str;
       example = ''
         [
@@ -107,13 +103,17 @@ in
       {
         assertions = [
           {
-            assertion = cfg.whitelist == null || cfg.blacklist == null;
+            assertion = (cfg.whitelist == null) || (cfg.blacklist == null);
             message = "Can't specify both whitelist and blacklist.";
           }
+          {
+            assertion = (builtins.length cfg.params) != 0;
+            message = "You have to specify zapret parameters. See the params option's description.";
+          }
         ];
 
         systemd.services.zapret = {
-          description = "DPI bypass service.";
+          description = "DPI bypass service";
           wantedBy = [ "multi-user.target" ];
           after = [ "network.target" ];
           serviceConfig = {
@@ -123,7 +123,7 @@ in
             Restart = "always";
             RuntimeMaxSec = "1h"; # This service loves to crash silently or cause network slowdowns. It also restarts instantly. In my experience restarting it hourly provided the best experience.
 
-            # Hardening.
+            # hardening
             DevicePolicy = "closed";
             KeyringMode = "private";
             PrivateTmp = true;
@@ -152,5 +152,8 @@ in
     ]
   );
 
-  meta.maintainers = with lib.maintainers; [ voronind ];
+  meta.maintainers = with lib.maintainers; [
+    voronind
+    nishimara
+  ];
 }