diff --git a/nixos/modules/services/monitoring/prometheus/exporters/varnish.nix b/nixos/modules/services/monitoring/prometheus/exporters/varnish.nix
index 5b5a6e18fcd..ede6028933a 100644
--- a/nixos/modules/services/monitoring/prometheus/exporters/varnish.nix
+++ b/nixos/modules/services/monitoring/prometheus/exporters/varnish.nix
@@ -45,7 +45,8 @@ in
     };
     instance = mkOption {
       type = types.nullOr types.str;
-      default = null;
+      default = config.services.varnish.stateDir;
+      defaultText = lib.literalExpression "config.services.varnish.stateDir";
       description = ''
         varnishstat -n value.
       '';
@@ -66,7 +67,7 @@ in
     };
   };
   serviceOpts = {
-    path = [ pkgs.varnish ];
+    path = [ config.services.varnish.package ];
     serviceConfig = {
       RestartSec = mkDefault 1;
       DynamicUser = false;