diff --git a/lib/modules/programs/systemd-networkd.nix b/lib/modules/programs/systemd-networkd.nix
index 10be7133..50a6f48d 100644
--- a/lib/modules/programs/systemd-networkd.nix
+++ b/lib/modules/programs/systemd-networkd.nix
@@ -11,6 +11,7 @@ in
         networks = mkOption {
           type = types.attrsOf types.attrs;
           description = "The networks to configure.";
+          default = { };
         };
 
         networkFiles = mkOption {