diff --git a/hosts/layne/services/apps/transmission.nix b/hosts/layne/services/apps/transmission.nix
index f4f1797..bd62e72 100644
--- a/hosts/layne/services/apps/transmission.nix
+++ b/hosts/layne/services/apps/transmission.nix
@@ -28,7 +28,7 @@ in
         "--lpd"
       ];
       settings = {
-        peer-port = 51515;
+        peer-port = 35994;
         rpc-bind-address = "127.0.0.1";
         rpc-port = 9091;
         rpc-host-whitelist = "transmission.labs.adtya.xyz";
@@ -54,4 +54,23 @@ in
     };
   };
   systemd.services.transmission.unitConfig.RequiresMountsFor = [ "/mnt/data" ];
+  systemd.timers.transmission-port-mapping = {
+    wantedBy = [ "timers.target" ];
+    timerConfig = {
+      OnCalendar = "*:*:00/30";
+      Unit = "transmission-port-mapping.service";
+    };
+  };
+
+  systemd.services.transmission-port-mapping = {
+    script = ''
+      set -eu
+      ${pkgs.libnatpmp}/bin/natpmpc -g 10.2.0.1 -a 1 0 tcp 60
+      ${pkgs.libnatpmp}/bin/natpmpc -g 10.2.0.1 -a 1 0 udp 60
+    '';
+    serviceConfig = {
+      Type = "oneshot";
+      User = "root";
+    };
+  };
 }