diff --git a/modules/nixos/_private/state/ports.nix b/modules/nixos/_private/state/ports.nix
index 092e1544..f8d4182a 100644
--- a/modules/nixos/_private/state/ports.nix
+++ b/modules/nixos/_private/state/ports.nix
@@ -55,6 +55,7 @@ in
             description = ''
               A set of ports indicating what goes where in the NixOS system.
             '';
+            default = { };
             example = lib.literalExpression ''
               rec {
                 gonic = {