diff --git a/lib/nixos/configuration.nix b/lib/nixos/configuration.nix
index 9ab14731..c9696b52 100644
--- a/lib/nixos/configuration.nix
+++ b/lib/nixos/configuration.nix
@@ -150,7 +150,9 @@ in {
   services.openssh.enable = true;
 
   # Open ports in the firewall.
-  # networking.firewall.allowedTCPPorts = [ ... ];
+  networking.firewall.allowedTCPPorts = [
+    9003 # xdebug
+  ];
   # networking.firewall.allowedUDPPorts = [ ... ];
   # Or disable the firewall altogether.
   # networking.firewall.enable = false;